RV Armor, rvroof.com, and Rhino Linings all have epoxy elastomer coatings (which are two part, mixed together at the spray head.) All three do a very good job of completely sealing seams and providing a UV resistant barrier that flexes, stretches and handles the road.
A RV dealer in my neck of the woods occasionally gets rigs with a spray on roof... they tend to be very good for leaks in his experience, although a large tree branch can tear it, just as with rubber roofs.
Were I buying a TT or a motorhome that had a rubber roof and keeping it for the long haul, I'd almost certainly have this done. RV armor keeps the existing roof, while Dave's Permanent Coatings strips the rubber roof and applies from the bare wood... more expensive, but might last longer since rubber roofs can come unglued.
