I think this game controls well for the most part, though I agree the combat could have been a little more refined. I've never accidentally walked off a ledge... if I remember correctly holding RB will have the Prince walk one step at a time. If you walk to a ledge/blade trap, the Prince will stop right in front of either. You need to make him move in order to go forward again.
If you're saying that walking and then trying to go down a ledge means you roll, you're running and not walking.