I made an engine demo sort of like this where you rotate the screen to move a ball around a maze. It used physics, and changed the gravity direction to always point "down" no matter where the screen was rotated. It worked perfectly.
I'll see if I can find the thing...
Well, I couldn't find the original, but it only took a couple of minutes to make it from scratch. It's actually really easy to do:
Just move the mouse left/right to tilt the maze. The important thing is that the gravityController sprite always changes it's angle to be the opposite of the layer angle. The gravityController is attached to the ball and force is applied to the ball in the direction of an image point on gravityController. Not too hard at all really, just a couple of events.