I am one of the believers that you should never have to lift any of the wheels off the ground. If you have a diesel motorhome you are putting an excessive amount of strain on the shocks and their mounts as that is about the only thing holding the suspension on at that point not to mention stretching the air bags ...... I would calculate the amount of slope and make some wooden runners that you can drive up on to compensate for the slope and leave your jacks up or just lightly touch the down to stabilize the coach.
It is never a good idea to raise the rear tires and loose the parking brake.
Steve