You can look for a hitch mounted swing-out spare tire carrier. I have run my spare on a roof basket on my old rig, and it was loud as a banshee and even worse, it killed my MPG. I know you plan on throwing your canoe up there, but I imagine it would only be up there during your trips. My ride was also my daily driver, so when I had my spare up on the roof the road noise and the loss of MPG were too much for me to stand. I can only imagine throwing a spare on top of a large SUV will be the same result. It will also be a pain and possibly dangerous trying to get the spare down when you need to use it. I had a pick up so I had the luxury of standing in the bed to get to the spare and that was still hard to do. On a burban, I could see a possible back injury in your future. The best place you can keep your spare outside of where the manufacturer puts it is behind the vehicle somehow. Like I mentioned, I had a pick up truck so day to day, I kept a fix a flat and a plug kit in the cab while the spare was in my garage, and during off road trips, the spare stood up in the bed against the rear window thanks to a few cam straps taking up precious cargo room.
When I got my new truck last summer, I immediately threw bigger tires on it with a slight lift. Thankfully, the truck is an F-150 and the spare well under the bed can accomodate up to a 34" tire so I just got a matching tire for the spare and now I'm golden. A hitch mounted carrier might be a good investment. It will keep the spare off the roof, and allow for throwing your canoe up there.