The Roof itself is a laminated structure, constructed the same way the walls are, aluminum. The radius portion of the front/back walls have wood rafters.
It is a one piece seamless piece.
Fiberglass layer, plywood, and then foam and plywood layer on the inside. The front and back spots with the wood rafters are filled with an insulation material.
I know the AC unit is braced and boxed in for support with aluminum.
In the pic you should be able to see the area that's boxed in for the AC and then of course the wood rafter portion with the curves. I really have no idea on spacing or anything though, soryr.