The structural load at the outermost edge of the cover must be transferred back to the wall. That can be done with cantilever beams that run back 12 to 15 ft into the house aligned with the attic joists or the roof rafters or with triangular side braces. The braces can be below the cover as in the photo or, if the cover is deep/steep enough, they can be part of the cover itself. The cover could also be high enough to be a part of the roof with rafters reaching up toward the ridge forming triangular side walls.

Otherwise, you need a skyhook.

Almost invisible support could be a tension rods or cables angled upward. A pair of them with stainless steel turnbuckles could look really cool.
Casey