Can my garage roof (truss system) hold a camper shell?

I design roofing systems for my projects, and you don't want to count on manufactured roof trusses to be able to carry any extra weight. I would add a pair of 2x10's parallel to the roof trusses that bear at the walls at each side. What I didn't see in your info was the span between walls. I can calculate what you would need to support your canopy if you can give me that information.