Think of it this way:
You can just rotate the background or choose to rotate a particular layer if you really wish.
Sounds like you want to rotate a layer or more.
To do this:
Event: Pick an Event, whatever will trigger your event.
Action: Pick the system object and "set layer angle".
Now when you do that special event, whatever is on that particular layer you picked should rotate. Of course your player can be on a separate layer so the player doesn't rotate.