Inspect from inside the house.
Climb as normal.
Once the trunks are below the top of the roof, anchor 2 climbing lines over the roof, to a tree or something suitable, on the back side of the house, with padding to protect the ropes as needed. Do not tie yourself to the trees.
Slide the pieces of trunk wood down the roof.
At some point the trunks Possibly will want to stand up on their own. The compressed roots may push them upright.
If they continue to lean against the house at the bottom of the roof, winch them upright and fell them away from the house.
Be aware that once the trunks are being cut shorter, even though they are lighter, they may start to push into the roof more, as the weight/ pressure may be pushing differently on the framing of the house. I have encountered this when I got below the top ridge of a roof. Apply support to the trunks with a winch or truck if the trunks want to sink into the roof.
You will need to keep away from the metal roof with your saw. Wedges can make space between the roof and wood. You might make some from wood that are thicker than felling wedges.
You will have some branch stubs stuck into the metal.
As you cut close to the roof with your bar tip, watch for wood saw- chips to change to bark saw- chips/ discharge.