Okay so I've been running my campaign for just over two years now and my players are currently level 13.

Recently one of my players pointed out that another player hasn't rolled below a 15 in anything for a while now. So I ask him to keep an eye on his rolls and let me know if it is just luck or if he is fudging rolls and sadly it turns out he is fudging his rolls. I've asked my other players that have also questioned it to watch his roll and call it before he does so he can't fudge it. 

I don't really want to confront the player and create a tension at the table so I just want to know if anyone has any ideas of a way I can tackle this issue? 

You've already created tension by informing other players and having them monitor the rolls for you.  If you don't do anything now that it's confirmed, you'll build tension with the group.

I would suggest not making a big thing of it; Give the player a quick message 1v1 - "If you're having trouble rolling accurately, I can assist by rolling for you."  See how it's received and if things change.

The group I first started playing with played on a small table.  Those of us, (me included), that couldn't keep the dice on the table had to use the dice tower.  Dice towers can be used for this issue as well.

Perhaps your table could implement a dice tray in the center of the table that all the players use, so everybody gets to see everybody's rolls. 

That way you could defeat the problem without necessarily calling out that one individual.

Players roll in public, where everybody can see them.

Quote from SamMc93 >>

I don't really want to confront the player and create a tension at the table so I just want to know if anyone has any ideas of a way I can tackle this issue? 

 
You don't need to apologise for stamping out cheating at the table, nor worry about negative consequences for ensuring everyone is playing legitimately. Ultimately, you're the arbiter of the game - and the other players will look to you to ensure this player is keeping everything above board - especially now they know he isn't.

But I totally appreciate your point. Calling it out at the table, mid-session, is going to cause embarassment and upset - which nobody wants. Cheating can be addictive, and there's a chance your player feels pretty ashamed by it, and would stop if you dropped him a quick private message, with as much grace as you can muster.

In future, I strongly suggest ruling that players roll out in the open, where not just you, but everyone can see it. There is absolutely no reason at all for players to keep their rolls secret - and will only fuel this kind of cheating speculation.

A final note - make absolutely sure this player is cheating before taking it further. This may just be a resentful player, annoyed at the good fortune of their team mate. I don't know the full situation - but perhaps simply instigating a rule that everyone has to roll in the open might nip this whole situation in the bud.

Confronting the player privately and making it clear (even if it's not true) that you don't mind that it happened as long as they stop will let them save face in front of the group, so if he's not a total ass he should be nice about it. And if he's a total ass, why play with him? You should be fine: it's not attacking him, it's helping him, it's giving him a chance. Then never bring it up again.

That said, "fudging" is cheating, and it needs to stop. Cheaters get booted. It's super nice of you to talk to this guy and give him a second chance!

Have a dice rolling tray in the middle of the table, or roll his dice for him, if he can't cooperate.

Dont put up with it. As others have said use a dice tower or tray. The player should be rolling where everyone can see his rolls anyway. Keep in mind he my be simply adding a bit to his modifiers to get the rolls he needs so you may need to look over his character sheet and take note of things. I had a player who was cheating his dice rolls and it actually effected the whole group. Long story short he no longer plays D&D with us anymore.  

I had a player who cheated like crazy on dice rolls years ago. All my players knew it, but the honest answer was no one not even me worried about it. We all had a good time, and had fun gameing so I let it go. I also cheated back and let the monsters hit him more often but he took that fine. I even made a comment like the monster must of had his luck. 

My suggestion is to decide if it matters? If so then a dice tray in the middle works best. Just say you read on a forum that rolling in front of everyone helps bond gamers or something. If you decide everyone is having fun at your table then let it go, and enjoy your story.

Quote from Veth13 >>

My suggestion is to decide if it matters? If so then a dice tray in the middle works best. Just say you read on a forum that rolling in front of everyone helps bond gamers or something. If you decide everyone is having fun at your table then let it go, and enjoy your story.

 Rolling on the table in front of everyone actually does create a sense of goodhearted tension and group bonding. One of my previous DMs trial-ran a Dice tower and by the end of the night all of us were usually leaning in hard on the table in anticipation of the rolls that would come out. Hell, we even made a short-lived mini game out of it during non-combat scenarios that played like Plinko from the old Price Is Right tv show.

And that is a great idea, and fun. A side game is bad ass. I figure if the game has been going on for 2 years, it's got to be doing a lot of stuff very right. So what's best for the game, calling out a cheater or letting it go? I mostly wanted to post a idea that was a little off the other posts and show a different opinion.

Side note I as a player love the tension that happens when everyone sees the rolls, I love the communal cheer when a crit is rolled or the collective groan when a nat 1 hits the table. 

Personally there is a lot of potential fun to be had at the "cheater's" expense without being confrontational or causing bad tension. Letting it go is an option, having the knowledge to adjust encounters and relevant checks versus their propensities to fudge their dice makes things interesting, and it is highly unlikely they will catch on unless they're into meta-gaming too. Even still, just being a goof about how you call them out makes all the negativity go away, even if they're a butt about it at first.

"Oh hey guys, new rule, you have to use the number on the top of the die you roll, can't just pick a random one on the side anymore."

Quote from Veth13 >>

I also cheated back and let the monsters hit him more often but he took that fine. I even made a comment like the monster must of had his luck.

 This is probably the funniest way to get back at them without calling them out.

I'm for either option, but I would see to it that it is as minimally impactful on the negative side as possible.

If you approach it in situation like “you’re cheating” it might be confrontational. If instead, you approach it as a poignant “you must have made a mistake....” it still points it out, but allows them to save face. “Making a mistake” is no big deal, “cheating” is a different matter. THEY will KNOW you caught them cheating, but politely chose to give them the “benefit of the doubt”. After having their “mistake” pointed out once or twice it will probably stop. 

 Another way to handle it is fudge your dice. But as a DM this would not be cheating. Just have it where everything hits and hits twice as hard to that cheating player's character. 

What happens to the group if the situation is left alone?  What happens to the group if the player quits after being confronted?  The answer lies somewhere in the middle.  One of the worst outcomes is the player is confronted and has to agree to behave but he never gets over it.  Simmering animosity can be very damaging and I would recommend kicking the player rather than put up with that.  But the player might be everyone's friend IRL.

If it were me and I was worried about the "drama" I would just make a slick dice tray for the players and another dice tray and tower for myself.  Then I'd expect the players to use the community dice tray.  The ones in on the secret would happily use it and the other should feel compelled to use it while playing your game.

I don't like dealing with Drama so good luck.

My group has everyone rolling in the open. Even I as the DM openly roll. Admittedly this has made some awkward scenarios such a patrolling guard being more of a threat than a BBEG,. But I get around that through narrative play and imposing unfavorable situations for characters such as getting knocked back, prone, loosing their flanking advantage, a strike turning into a grapple. Just something to keep a threat real when my bad guy I've been setting up decides to roll below 10 for multiple rounds in succession.

Quote from FTT >>

My group has everyone rolling in the open. Even I as the DM openly roll. Admittedly this has made some awkward scenarios such a patrolling guard being more of a threat than a BBEG,. But I get around that through narrative play and imposing unfavorable situations for characters such as getting knocked back, prone, loosing their flanking advantage, a strike turning into a grapple. Just something to keep a threat real when my bad guy I've been setting up decides to roll below 10 for multiple rounds in succession.

Quote from FTT >>

My group has everyone rolling in the open. Even I as the DM openly roll. Admittedly this has made some awkward scenarios such a patrolling guard being more of a threat than a BBEG,. But I get around that through narrative play and imposing unfavorable situations for characters such as getting knocked back, prone, loosing their flanking advantage, a strike turning into a grapple. Just something to keep a threat real when my bad guy I've been setting up decides to roll below 10 for multiple rounds in succession.

 As a DM you should be rolling behind a screen or in a way that the players cannot see your rolls. 

Quote from BrokenDM >>

 As a DM you should be rolling behind a screen or in a way that the players cannot see your rolls. 

 
That's not true. While common practice is to hide rolls, keeping things hidden is just another option for a DM to create tension, by being able to adjust things accordingly. Also known as 'fudging it'.

I know of a few DMs that roll in the open, not just for their own enjoyment of 'rolling' with the consequences, but because they never want their players to feel anything is fudged. That just the way they play, and I applaud their skill in being able to manage it.

Quote from Chequers >>

Quote from BrokenDM >>

 As a DM you should be rolling behind a screen or in a way that the players cannot see your rolls. 

 
That's not true. While common practice is to hide rolls, keeping things hidden is just another option for a DM to create tension, by being able to adjust things accordingly. Also known as 'fudging it'.

I know of a few DMs that roll in the open, not just for their own enjoyment of 'rolling' with the consequences, but because they never want their players to feel anything is fudged. That just the way they play, and I applaud their skill in being able to manage it.

 I like to stand and walk around while I DM, so I frequently tell my players to randomly roll and tell me the number. They KNOW I’m not fudging because they rolled the die. I always make a point of sitting down ahead of time before a roll that I might need to fudge (usually combat “because I need the NPC/monster stats”) so they never wonder why I make those rolls. After that I go back to standing and having them roll for me. So far they have never accused me of ever fudging.