I've been brainstorming some joinery possibilities for connecting the common rafters on the shed (lean-to) to the top plate. I put them all into one example. I think the tusk tenon is the winning candidate at this point. In the first picture, I've widened the top plate from a 7x9 to a 10x9 to better accomodate the rafter joinery. While this might not be necessary, I could enlarge this plate...and this shows how that would look.

NOTE: The last picture shows the most recent revision, which is much more simplified. I believe it solves a lot of obvious problems with first designs.