[carpdad]

Minimum pitch needed for a shingle roof is 3 feet for every 12. So if you want the porch roof eave to be about 8', you need your rafter to be that high. First a header flat across the rafters, rafters out to the eave header then cleat supports between wall plate and the rafters. If the cover is 10' out from the wall, 16' 2x6 could be enough or pieced above those cleats. If pieced, it may be better to add a little knee wall over the outer wall.