Newmar uses what they call Brit tek roof it's on tough roof.
I think on the real high end Newmar,s you can have fiberglass.
My new to us 2008 Newmar has the brit tek roof it's on great shape other than the seams which I cleaned out and re did.
Even Fiberglass roofs have seams to caulk.
One big difference I noticed between the fiberglass roof on our Gulf Stream was noise. When it rained hard the noise was extremely loud.
Not with the brit tek roof. It's quite in the rain.
PS I'd never own another Goof Stream product.