For the roof I think I would go with rolled roofing over plywood, it doesn't shine like metal and you can get it in what ever color your surroundings are. You're local lumberyard or home center should carry it.
I'de do that then get those grassy "tarps" to cover it to make it blend in even better from above where the ducks will see it.
we'll go down here, this blind is an hour north and not nearly as many ducks. blind looks awsome though