Insulation help for my garage with pics

insulate roof foam baffles ventilation - YouTube

They also make these, simply staple in place and then install your insulation.

http://www.jrproductsinc.com/shop/pc/Cardboard-Attic-Baffles-24-x-33--50-per-bundle-288p201.htm

You can install some vents on the soffit for air flow.

I tried using those in the house, what a pain in the arse on a retrofit!! F'n roofing nails in the back, neck, skull!! On a new build for sure, or in the garage, but I gotta do a test hole on the soffit and see whats underneath the soffit first. Its gonna have to wait till spring as my rafters are like my bowels....LOADED!!