Last night, our group encountered some vine, needle, and twig blights.  The wizard decided to cast Flaming Sphere, and despite my best efforts, I am not sure if we ran the spell correctly.

First, if you ram the Flaming Sphere into an individual creature, does the spell require an attack roll, or just the DEX save of the targeted creature?  We used just the DEX save.

Second; the wizard has an initiative of 15 and the blights collectively have an initiative of 5.  On the wizard's turn, she moved the sphere to a square that is 5ft from three of the blights.  When it is their turn, can't the blights just move away from the sphere and not take damage?  Technically, the blights ended their turn after they move away from the sphere.  If that is the case, any enemy with a lower initiative would simply move away from the sphere since the wizard acted first...so much for her having the higher initiative.

Spells do what they say, and don't do what they don't say. That means:

- If the spell required an attack roll, it would say so. So you played it correctly by just using the Dex save. It's very rare for a spell to have both an attack roll AND offer a saving throw. I can think of Disintegrate, and probably a few others, but most of them are only one or the other.

- The spell says damage happen if a creature end their turn next to the sphere, so they could indeed escape by simply moving away. This is definitely working as intended, Flaming Sphere is only a 2nd level spell, and does not seem designed to be able to hit several ennemies. 

Initiative doesn't actually matter here, since enemies would have their turn to react to the sphere having stopped next to them anyway.

Hope this helps!

Concerning the first part of your question, Flaming Sphere only requires a Dexterity save from the affected target(s). To quote Jeremy Crawford, "If it required an attack roll, it would say so" :p . As a rule of thumb, an action usually only requires one d20 roll to determine effectiveness; an attack roll or a saving throw. Exceptions exist, but they're pretty rare.

The second part of your question is mostly spell design. A spell that has an area of effect and lasts more than one round usually has one of two ways to affect targets: at the start of their turns (and often without other means to control it), or at the end of their turn (and usually with a means to force it into a target or targets). Flaming Sphere is on the second category.

That means that you can leave the sphere in an area, but most opponents will try to move away from it (unless they are stupid, mindless, immobile, grappled, restrained, etc.) You have the option, however, to move the sphere directly on a target to force a dexterity save there and then.

Note that initiative is mostly irrelevant for this matter. Even if the wizard played after the enemies, and moved the sphere near them, on their next turn they would still be able to move away before damage was applied.

For an example on the other way to affect targets, see Blade Barrier which affects targets at the start of their turn if they are in the area (or when they first enter it in a turn), but is immobile at the point of its casting.

I totally agree that a 2nd level spell should not be too powerful.

So, even if the wizard had the lower initiative and moved the sphere after the blight's turn, the blights within 5ft don't risk damage until the end of their next turn?

Yeah, basically you can use this spell as a bonus action to deal 2d6 damage on a creature within 30ft, or you can use the sphere to deny access to something, since enemies can't go through it. 

The spell is only summoned into an unoccupied space. It is concentration spell you can use a bonus action to attack targets with every round, per the description, you can move it right into them to trigger a DEX save to determine full or half damage.

I agree with everyone else about both problems.

An ally could grapple the target to keep them from moving away from the sphere.

Thanks everyone.

As mentioned this spell is mainly used to ram into someone once per round as a bonus action.

The damage at the end of enemies turn is typically  intended to use this in conjunction with fighting something in melee range, especially if there's two people.  Have one player next to the enemy with the flaming Sphere behind the enemy, and another player beside the first player (diagonal from the enemy.). On the enemies turn, they can either try to move away and thus take an opportunity attack from one of the two players, or stay put and take damage from the sphere.  

Or, as DxJxC mentioned, you or a party member can grapple them next to it.  This is particularly handy for a Circle of Moon druid since you can cast this spell and then Wild Shape into a creature with enhanced grappling capabilities.

It's a pretty handy control spell too, since obviously enemies are going to try to run away from it.  Have a bunch of enemies behind a wall shooting at you?  Move this spell around to them to scare them all out; since you can cast the spell 60 feet away and then move it 30 feet, you can force enemies to move from quite a distance away.  

P.s. as far as I know there aren't any spells or abilities that require both an attack roll and a save.  The affotmentioned Disintegrate does not require an attack roll, just a Dex save. 

How do i delete this?

And I assume that moving it as a bonus action still allows for casting any spell of 1 action so you can ram someone for damage and cast a spell for damage too, as long as that isn’t concentration as well.