Our Roadtrek dealer strongly recommended Meguiar's Premium Marine Wax for protecting the roof. This is specifically made for protecting the gelcoat of the fiberglass. It was easy to apply. After 8 years, it seems to be doing a great job of protecting the roof.
The pressure recommended on the Roadtrek sticker inside the kitchen cabinet door recommends 50 lbs front and 80 lbs rear. The dealer had them at 80 when I bought it. He said it would work fine and give me the best gas mileage. This gave me a very hard ride. I eventually tried the recommended 50 lbs in the front tires. This gives me even more of a "car-like" ride. Very comfortable and handling remains perfect. I have not noticed any appreciable drop in gas mileage which averages 15 mpg. I've decided to keep my tires at 50 in the front and 80 for the rear. Incidentally, the Roadtrek rides better and is quieter than our Honda Odyssey minivan.
Note: Tires are designed to run at a specific pressure for a given load. If you underinflate, then the tire will run hotter and have a decreased life, plus your gas mileage will go down. If you overinflate, the area of tire in contact with the road will decrease, causing less friction between the tire and road. This will increase your stopping distance and decrease the tire's ability to hold the road when cornering. For safety's sake, keep your tire pressure close to what is recommended on your vehicle door.