John W, you may like to consider solving your heat problem by covering the rafters with a SIPS layer before fitting the new roof.
SIPS are a sandwich of polystyrene with oriented strand board or plywood on either side.
A SIPS roof works because there is no direct connection between the surface exposed to the sun and the frame of your home.
At the moment the type of insulation you have, while doing a reasonable job of keeping you warm in winter, does not stop the heat from reaching the inside of your home, this heat mainly arrives through conduction.
A five inch layer of polystyrene, that is 98% air and 2% plastic will stop this heat movement by conduction making your home a lot more comfortable.
Once you have done the roof, think about doing the south facing side/sides of you home.