Have you concidered metal roofing panels? Sort of like a barn roof. I think it would be much faster, use less strapping and will likely last as long. You can order custom lengths, profiles and colours from most building supply stores. You can also order any ridge caps and flashings required. The sheets are usually 26 ga, primed front and back with a satin topcoat. You can also order color match screws with the proper rubber washers already attatched.
Other benifits are: you can walk on a metal roof afterwards, (not advised with steel or aluminum shakes) and the snow usually slides right off with sunny weather. (if thats even a benifit..) Hope this helps.