I'm sorry about the year-and-a-half bump, but this page is the first Google result for "nook touch change screen rotation". I have made an app for rotating the NOOK screen, and just about anything else's screen too. You install the app, and when it launches you are presented with two buttons: Portrait and Landscape. Click one and the app exits, sticking the screen in the new mode. Enjoy!
Oh, and you have to change the ".zip" to ".apk" for it to work, I can't upload apk files here, and it IS technically a zip file anyways (the admin should add apk to the list of good formats.)