I really think I would just use a mild soap, such as Dawn, to avoid possible damage. I've never figured out the big deal of getting a rubber roof extra super clean anyway. I used to think the black on my 1999 rubber roof was mildew or something but then I found that it's just the underlaying black layer showing through due to wear of the top white layer. Cleaning isn't going to fix that. We did have an RV dealer apply a prime coat and a topcoat of some sealer hoping to get a couple more years out of the roof. $400.