I read the rules on sneak attack and it says once per round. What if the rogue uses an area effect power (like blinding barrage)? Does each person in the area effect take the sneak attack damage or it is just one of them?
Once per round, when you have combat advantage against an enemy and hit that enemy with an attack that uses a crossbow, a light blade, or a sling, the attack deals extra damage. If you have dealt Sneak Attack damage since the start of your turn, you cannot deal it again until the start of your next turn. You decide whether to apply the extra damage after making the damage roll. As you advance in level, your extra damage increases.