02-24-2013 08:59 PM
02-25-2013 04:30 AM - edited 02-25-2013 05:17 AM
Having reread this I now realise you have been rejected for not handling rotation correctly, rather than as I first read your title being rejected for an app that does not support landscape.
This is easy to do;
OrientationSupport.supportedDisplayOrientation = SupportedDisplayOrientation.DisplayPortrait;
You didn't say what SDK platform you chose but this can be done through the apis for that platform found in the documention just search for orientation.