New Studio Setup, Need help setting up my studio Options

[sumusic]

Here is a breakdown of my equipment:

iMac (DV) w/ Harmon Kardon Sound Sticks and iSub
Midisport 1X1 interface
Cubase VST
Casio CTK 601 keyboard (it does the job)
Roland JV 1080 w/ Orchestral II and FX expansion cards

I have tried several configurations to set this up, but nothing has worked . How do I use the keyboard as the controller and record the JV 1080 sounds into Cubase while listening to the finished product through my desktop speakers? Do I need to download software for Cubase VST to recognize the JV 1080?

Any help is greatly welcome!