I have a stack in the trailer tied down to an anchor point, with the rear rim on top of a full size car spare and trailer spare. The front rim is separately propped up against the stack and tied down. None of the rotors touch this way.
Back in my racing days, we had a shelf across the front of the trailer. There was a steel bar about 12" above the level of the shelf and blocking the wheels so they stay up on the shelf.