Bank change is a control change, just like modulation and damperpedal.
The Roland synths use CC 00 (Control Change nr. 00) for bank change.
The value is 80 and up, and depends on how many banks that you have.
Bank change is channel specific and must be sent a little before the actual program change.
Roland synths changes the sound when it recieves a program change, the bank change will not take effect untill it gets a program change.