RV roofs get dirty. Here's how I clean mine
The top of your RV needs to be cleaned periodically. A clean roof keeps the sides of your RV cleaner and it allows inspection of caulk seams and flashings. My RV has a ladder and is built so I can walk on it without worry of damage.
A bucket and mop will suffice but I found the same product I use to clean and wax the sides of my RV works as well on the top. Note, I have a fiberglass roof. If you have a roof made out of a different material, use a product appropriate for that purpose.
I use a waterless wash and wax system called, “Wash Wax All”. It comes from the Aerospace industry and I’ve used it now for a couple of years on my RV. It pretty much works as advertised. I suspect the other waterless wash/wax systems from Meguiars, Chemical Guys, Mothers, etc. work just as well.
The two-headed applicator is the key to going fast. Squirt the “Wet” side with Wash Wax All, apply, flip to the “Dry” side and rub off. It goes quick and the results are excellent. Another advantage is you don’t need to haul a bucket and hose up to the roof.
Below are a couple of videos of before and after.