I just called The local income tax office and they said you have to registered as a sole trader to use ROS online and a PAYE person must used the paper based form....
I believe you should fill a Form 11 (the short version should be fine). It's likely that with at least 8 months rent that you are over the threshold for a form 12, if that is even an option now that you're no longer PAYE (assuming you were).