You need patches. I guess the port 0 is an external midi device. If you don't have such a device, you have 2 options: you can load a patchset into your soundcard if your soundcard supports this(check sf2load). Then if midi is sent to that soundcard, you will hear it. You can install 'pmidi' and do a 'pmidi -l' to get a list of available midi ports. Another option is to use timidity, which is a software for soundcards who do not support loading a patchset into the card itself. You can then start timidity in server mode, and you should see extra ports in 'pmidi -l'. You can then use those in Rosegarden.