I glued the front roof panels and after they dried, I glued the scrapbook paper panels on top. Before I assembled the roof, I had traced the shapes onto the scrapbook paper to get the alignment of the "tiles" the right way. Thank goodness I did, the assembly was very easy. I painted the undersides of the panels Festive Green to match the walls.
Still pondering how to finish off the edges and corner joins nicely. Suggestions are welcome!