As part of our trailer dent repair of the rear 5 skins we decided to apply a roof finish that is also a sealer.
In researching the three chemical types (acrylic, silicone and epoxy) I decide on the catalyzed epoxy type which has a harder surface finish to support walking on it. Product: NovaTuff RC-100 Flexible Epoxy Roof Coating, made in Texas.
Here is two images of the first coat. I purchased 3 gallons for this 25 footer. I think 2 gallons would have been OK.
The next step will be to clear coat from the beltway up. The rear four panels have been stripped, you can see how the upper sections the clear has failed, near the beltway however, the finish looks good.