I use a mild car wash detergent twice yearly for the roof. I also wax the sides twice yearly but not at the same time. I hate waxing so I do part of it and take several attempts to get it done. I use a good car wax - right now Meguiars. I do NOT wax the rubber roof.
Dan & Christine (and Molly)
2015 GMC Sierra 4WD Crew Cab Short Bed with Max Trailer Pkg
2015 Jayco White Hawk 27 DSRL