The limb is gone - I had it removed yesterday. I had no idea what size it was until I got home. I stopped on my way out of Minneapolis on Monday morning and bought a 16" chainsaw (electric) like I had 10 years ago when we first moved here and the yard needed clearing work. Well, when I saw the limb on the roof and how far it was up in the air, I knew that my little Barbie chainsaw wasn't going to be enough to nibble away at that giant - it would have taken days of work!
It's all done and there appears to be a little shingle damage and everything else is fine. I think the wind cracked the limb at the trunk and it came down rather slowly, peeling away from the main tree. Thank goodness!