When I'm on the road, rain takes care of cleaning the roof. At home, the RV lives inside a building that I own. If there are streaks on the sides when I get home, I use a long handled soft brush and a hose to remove them while I'm washing the bugs off the hood and overhang. The only time I've ever washed the roof was at an RV park that had a hose attached to a water pipe and a moving platform to climb up on. And that was in Yukon Territory on my way to Alaska. And the roof wasn't that dirty.
If anyone climbs up a ladder here at home and complains about the dirty roof, I'll be happy to hand them the long handled brush.