I do some of each. When I am deciding which character to attack at random, I roll in the open. Most combat I do behind the screen as to hide what modifiers my monsters have to keep up the mystery of how strong or weak they are. I do allow them to check my rolls if I am unusually high or low, but I never fudge nor do I let them.
I roll mostly open, but there are some exceptions.
E.g. I like to roll "Perception", "Insight" and "Investigate" checks for my players. They give me their modifiers, I roll behind the screen so they don't see what their result was.
That is something I grew accustomed to during Shadowrun, and I think it's a nice way to avoid having every player around the table chime in to "also look around" when the first one rolled low and didn't find anything. The other players are still allowed to look around as well, but they won't meta game it anymore because the know the first roll was bad.
Another kind of roll I usually do behind the screen are attack rolls of my monsters. I am not afraid of having a PC die in a tough combat, but dying because a Bandit Captain rolled 3 Crits in a row on his multi attack? That is just stupid and not very satisfying. First one is a crit, the other two are normal hits. The PC is still close to dying, has likely failed his first Death Save already, but the other players can still react and try to save him.
I do some of each. When I am deciding which character to attack at random, I roll in the open. Most combat I do behind the screen as to hide what modifiers my monsters have to keep up the mystery of how strong or weak they are. I do allow them to check my rolls if I am unusually high or low, but I never fudge nor do I let them.
I roll mostly open, but there are some exceptions.
E.g. I like to roll "Perception", "Insight" and "Investigate" checks for my players. They give me their modifiers, I roll behind the screen so they don't see what their result was.
That is something I grew accustomed to during Shadowrun, and I think it's a nice way to avoid having every player around the table chime in to "also look around" when the first one rolled low and didn't find anything. The other players are still allowed to look around as well, but they won't meta game it anymore because the know the first roll was bad.
Another kind of roll I usually do behind the screen are attack rolls of my monsters. I am not afraid of having a PC die in a tough combat, but dying because a Bandit Captain rolled 3 Crits in a row on his multi attack? That is just stupid and not very satisfying. First one is a crit, the other two are normal hits. The PC is still close to dying, has likely failed his first Death Save already, but the other players can still react and try to save him.
I also rolled 3 20's in a row last October. Everybody saw it and 2 guys took pictures.
I tend to roll in secret, but when I do fudge the rolls, it is always in the players benefit.