I have my entire interface in one Storyboard. How can I make most of the ViewControllers only support a portrait orientation while only a couple supporting all orientations.
You should watch the WWDC'2012 videos especially the ones in the "Essentials" section talking about rotations.
The one called "T Evolution of View Controllers in iOS" explains the subject about rotations (and how to make them compatible with various iOS version) in great details, with explanations and code samples, and I couldn't explain it better than Apple ;)