Look into a RV wash guy that would come to the RV park or even to your home and just do the roof for you every so often. If the cost is too high for a complete RV wash perhaps they'll just do the roof for you and then you do the wash but you'll have dirt running down the sides if you don't tackle the sides as soon as he leaves.
The panels do need cleaning every so often. Rain doesn't do it.
I think being on a ladder or any other platform/device and trying to reach the panels would be more dangerous than just getting up there. If your panels can be reached just by climbing your RV ladder and walking down the center of the RV it's safe as long as you don't have to walk along the edge.
At some point one needs to get on the roof to check all the caulking and roof surface to maintain your RV in good condition.