No need to be complicated. Now got PU metal roof. So, no need to add fiberglass whatever. Google for something like this

http://www.haipoint.com.my/roofing/pu-foam-and-metal/

I think now many companies manufacture this. It is not about supplier but find good company that can do good job. Find company that do roofing and ask if they have this type of PU metal roof. Probably most do this now.

Last time only metal and I was reluctant to use on patio. Now I used this and very satisfied. I can walk on it without even denting it.