What "3/4 inches are you referring to? And how are you planning on getting wrap or R-board 'in that 3/4"'? And what does the roof have to do with the siding and house wrap? And what size and how about what???
I'm real sorry for sounding so confused but I am. Maybe someone else isn't. In any event, if you don't get an answer on your original post, come back with more info.