Progress report: This has turned into quite a chore. I started by sweeping and removing the loose gravel. Then I tried to cut a strip as suggested by Robert without much luck. I tried several tools to make the cut, an edger, an ax and a circular saw, but nothing seemed to work. I then tackled the roof from below. I set the depth of cut to 1 1/4" on the circular saw, and cut the decking between every other joist. I then braced the joists and using a chain saw cut the joists in 8' lengths. When I removed the bracing I expected a section of roof to fall. No luck. After a few minutes of prying, the joists with the decking finally fell, but the tar paper and about an 1" of some type of black 4' x 8' sheets of insulation board remained. I removed a section about 8' by 16', prying each set of joists and decking until it fell, but the tar paper and insulation board remains in place. I plan to try the chain saw on the tar paper and insulation board today.