Rubber roof cleaning
You can use something like simple green with a scrub brush. Let is dry thoroughly. Then apply a product by Dicor for rubber roof sealing. DH taped off at the edge were the roof meets the side of the trailer with blue painters tape. Follow all directions on the product can. After you have applied the second coat of roof sealer immediately remove the tape. You can get these products at an RV store. If you aren't near one then search the internet for the best price. I usually get this in a gallon size. It keeps very well. Another product is Kool seal.These products have to be applied in the shade or when the sun has gone down.