Personally, I wouldn't feel comfortable trying to secure a propane tank on a roof rack. Most roof racks don't have very high sides, and the tank will be somewhat of a top heavy load to secure. I usually carry mine in the rear 'trunk' area. I always use one of the tank base stabilizers to help keep it upright, especially with the OPD equipped tanks which do not like being transported on their side. Another option, if you are not using a trailer, is one of those hitch mounted load platforms, as long as no one hits you in the rear. :scared: