They have sealing systems that are intended to protect/restore the rubber roof. You will get mixed responses over how well they do that but they do typically make the roof nice and white at least for a while.
As with any paint, follow proper prep if you want a reliable end product.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV