Make sure the mac is happy with the synth as per Jerm's reply in the other message about the mac's audio/midi setup.
Then go to metro's MIDI SETUP and allow the Roland to record.
You can then go into the MODIFY OUTPUTS AND BUSSES and allocate tracks to the Roland.
Then download the program names for the roland from
http://www.cakewalknet.com/images/instrumentdefinitions/XP-80_ins.zip
Open the PROGRAM NAMES menu option and install them and you should be able to list the instruments in the graphic editor and tracks windows under Bank and Pgm. names.
When all up and running SAVE PREFS!