@Jo_Ann
So far I can't even duplicate the partial success that you had. I extended the second floor over the garage, creating an "attic room" with a ceiling height of "0", but no joy with the roof. I'm starting to think it will require features that are not available in HD Arch.
Also, did you do something special to keep the hip roof over the "bumpout" in the back of the house to not extend all the way to the top ridge? I need it the way you showed it but mine is not behaving that way.