There could certainly be scum power roles. The scum already know everyone’s alignment, but they might have a Role Cop that can check to see whether townies have power roles. A Doc probably wouldn’t do them much good, and a Vig would be very overpowered for scum. But roleblockers, watchers and trackers work well for both sides. There are also some scum-specific power roles such as the Godfather, who shows up as Town on Cop investigations (I would consider it borderline unfair for the Mod to put such a role in the game without warning us, though), or a Tough Guy, who can override Doc protection to kill a victim.