I use orange Ajax liquid. It does a great job and does not harm he environment. I use a soft bristle brush on the hard to clean areas but most of the roof comes clean with our sponge mop. Rinse well with a hose. Even with removing and replacing the two weather protectors over the vents the whole job takes less than an hour.
I use Dawn Dishsoap and water with a softbrush to wash the whole RV. Then 303 protectant on the roof and a cream wax I got from my RV dealer last year (can't remember the name and in storage now)