My manual also says I don't need to do anything. But I do clean it at least once a year if for no other reason than to reduce black streaks.
I use a diluted concentrate called
Voom. Made for RVs, it's the best cleaner I've found for awnings. It's pretty good for roofs too, although I've had slightly better success cleaning my roof with a mix of Oxyclean and hot water.
I have never conditioned my roof. Our previous trailer was 10 years old when we traded it and aside from some tree sap stains the roof looked like new.
