Stainless steel fasteners should be used for doors windows and exposed stuff. Stainless steel is not just one quality. Do you buy the “big box store” quality or professional quality considering we are in a highly corrosive environment.
Rebar can have coating to prevent rust and spalling. What is the difference in cost and do local contractors approve of and use coated rebar? Black rebar is rebar without any coating. The image at right can show relative pricing. I think I would use coated rebar on the roof.