I think roland uses a proprietary format. If so, unless they make a conversion tool, you'll have to play them using a Roland device and record them as wav files.

of course, Roland do use a proprietary format :) powerful and versatiles softwares like KONTAKT by Native Instruments are capable of reading it, but I cannot spend so much for just that reason. I also know that there are some softwares that are designed only to convert those formats, but they cost too much too.
I wonder if there is a cheapest way :)