I am assuming you mean there is a white ring around your rig on the ground? Which means when it rained, the white coating on the roof came down the sides of the camper and made a "ring" all around the camper. If this is the case, you probably should think of treating your roof with rubber roof sealer. It's a rubbery substance you brush or roll on your roof, like paint, it dries and becomes a new rubber layer. It's not cheap though, but it's a lt cheaper than replacing the entire roof.
You can probably get another year or 2 out of it before you should treat it. But if you treat it now, it would be better.