The reason I've never been a Rosegarden user is because I've never found anywhere in the program where you can do generic (non-GM) Midi.  I do mostly very electronic stuff where the idea of banks and presets that have to be assigned to a particular instrument sound with a well known instrument name isn't very useful to the kinds of patches and samples I'd use.  But there doesn't seem to be anywhere in Rosegarden where you can just do regular ad hoc this-bank/program-is-whatever-I-say-it-is style Midi.