George Nez pioneered and wrote the book on hypar roofs, along with Albert Knott. They’re extremely durable and practical, and have been used around the world for decades. This is the same type of roof used on the Free Burma Ranger Clinic posted earlier.
The basic process involves building a wood or bamboo frame, stretching nylon plaster mesh over the frame and stapling in place, and then coating the roof on both sides with a slurry of Portland cement and latex/acrylic admix. FlyingConcrete has more information on their site. Or you can buy George Nez’s book Latex Concrete Habitat at Amazon (currently $18).
Roofs for the World
Image source 1&2: Nez Roof Construction 8/2004
Image source 3: Ben Vander Plas
Video of George Nez explaining the concept
Flying Concrete http://www.flyingconcrete.com/hypar.htm
Free Burma Ranger hypar roof album
EarthbagBuilding.com project page about the Free Burma Ranger Clinic