### Roll once. ###

Roll the damage once. For *Thunderwave*, this would be a number of d8 dice depending on the slot you used to cast the spell. Once you total up the damage, apply it to each target of the spell.

From the *Players Handbook* p 196, in the "Combat" chapter:

>  A spell tells you which dice to roll for damage and whether to add any modifiers.
>
> If a spell or other effect deals damage to more than one target at the same time, roll the damage once for all of them. For example, when a wizard casts fireball or a cleric casts flame strike, the spell's damage is rolled once for all creatures caught in the blast.