Hi, Jay Stang - w/r to changing roof pitches for porches, Chief Architect training has a great lesson available on YouTube - I think if you look for the session about 1 1/2 story houses you will find it. It says that it's an hour and a half long, but she really only is presenting for the first hour and a half, and she's very, very good.
Another way to do it is by copying your roof in place and breaking it up into two smaller planes. A little trial and error, but I thought it was fun and I got the hang of it relatively quickly.
Good luck!