Best way to insulate this?

Hi all,

Attached is a photo of my issue. I have a gambrel style roof (which is unvented), and cedar TNG siding. The intersection of the roof line and the TNG siding leaks a good amount of heat.

My plan was to (1) great stuff spray foam the seam, (2) cut and glue on a wedge of XPS foam, (3) get some 8” siding sheets and run them horizontally from the side of the roof to the wall, essentially creating a channel to hide the insulation. I would then fill in any extra space in the channel with rock wool.

Thoughts? Ideas?