So once again we got the big John Deere mower and the lawn tractor out of the garage, moved them over to the old house, and used them as anchors for the safety rope. We moved ladders into place. Lisa got into her safety harness and climbed up onto that roof carrying her trusty hand saw. She spent the next three-plus hours in near-freezing temperatures trimming foliage from the main trunk of the fallen tree to try and lower the total weight. Then she started cutting sections from the tree about a meter or so at a time, allowing the tree to fall only a short distance each time. That tree is tough! It was a hard slog cutting it, even undercutting properly and with the tree's own weight pulling it apart.
I mainly stood around and stamped my feet and rubbed my hands attempting to stay warm. I wished we had the burn barrel going.
Having "walked" the tree about two-thirds of the way down the roof, Lisa (not surprisingly) ran out of oomph. Moreover, the freezing fog, which had never gone very high, was descending again and had reached the tops of the trees. I insisted that she come down from there before she ran out of enough energy to do so.
That last piece of the tree is very challenging. There's no room to work with it where it sits on the roof. Lisa says we may have to give in and call on a professional tree-removal service to come out and cut and remove the rest of it.