I'm not sure if this is true everywhere, but the Michael's where I live (San Diego) sells a line of diorama products called "Missions of California" for modelling old Spanish missions. The scale is a little off from Malifaux BUT, one of the products in the line is a thin plastic sheet molded in the shape of spanish style roofing tiles. All you would need to do is cut out the right size, maybe build some sort of support underneath to give it an angle, and paint it up.