We recently bought a 3008w with the Diamond package, I had the same questions you did. I was up on it Sunday installing the vent covers and was impressed by the roof. It is called Superflex and it is made by AlphA systems it is a membrane and only needs cleaned a few times a year. Top job or SpicnSpan are recommended. The paperwork says not to treat with UV protectors because it may damage it. I checked out their website for more info, www. Alphallc.us pretty impressive stuff, better than the roof on our previous trailer.
2012 Ford F-350 Lariat Crew Cab 6.2L FlexFuel
2014 Rockwood Windjammer 3008W