I was wondering about that. I don't know how to tell Rosegarden what to use. I don't see it in the settings, just the Jack transport option.You should set rosegarden to use jack
Also I tried to load SoundFonts instead of just using MIDI, and failed miserably. But I suppose Jack will be able to handle SoundFonts as well as MIDI if/when I get Rosegarden to work, correct?