Line-X for roof

Line-X comes in various colors now, just more $$$ over black.

Seems like that black would get really hot though.

I'm leaning this way when I need to have it done:
http://rv-armor.com/index.html

Yes, it is a real thing. The old roof is removed and very good prep is required but some dealers doing RV roofs are offering lifetime warranties.

The only issue is weight. On my previous long box Ram 2500 Line-X added about 80-lbs. Once you know the square footage of your roof, you'll be able to figure out roughly how much weight it will add; likely a several hundred with a large roof.

Moved from Campgrounds to DIY

Several years ago when I had my truck bed sprayed the business that did it said they had just done a trailer roof. First one they'd done. They said they thought it would work out pretty well and were talking why didn't trailer manufacturers use a similar process. Don't have any idea how it worked out.
A guy who use to work for LineX locally has a late 90s Dodge 1/2 ton truck that he's sprayed the entire body with LineX. Can't say it's the most attractive truck I've seen but he said it helps quiet road noise and doesn't get parking lot dings.

These days there are many liquid products intended for
RV roofs why use something intended for a truck bed?

Yes, it has been posTed before, do a search.

And you might get more hits if you post this type of question in DIY forum.