Dormer style with outside wall the same plane with the house outside wall (pic)

[Elovia]

Matt,

Select the interior walls that you created to make the dormer and open their Wall Specification dialogs. On the General tab, put a check in the "Invisible" box; this will turn the walls invisible and keep the roof structure while allowing you to see through them for interior camera views - that is, if you're still working on the roof lines. However, as JoAnn suggested that once you're finished creating your roof, turn off the Auto Rebuild Roof option in the Build Roof dialog, and then you can simply delete those walls. If you find that you'll need to change something about your roof, or rebuild it, then you have several options because you're using Pro. You can either manually create new roof planes, or modify existing ones, or you can make sure the walls are in place (invisible or not) and have the auto roof generator take care of it.

Good luck.