R-bus is only compatable with other Roland products. It is a digital format.
The optional output cards will send adat or aes and spdif.
If you are using a 2480, you might as well not even bother with the preamps. There is no way to get around the preamps in the unit, the line inputs are just routed through the preamps with a pad. You would be funneling good sound through the crappy front end of the Roland, don't waste the cash.