I use a Teac SCSI CD-Rom with a S760 and a Adaptec SCSI card, reading S700 Series CD-Roms thru my PC (works with S750/760/770 & SP700). It also has capability of Convert load Roland W30/S550 and Akai S1000/S1100 libraries. I don't know about S770 having this feature.
Roland U.S. has a compatibility guide at:
http://www.rolandus.com/SUPPORT/DOCS/SUPNOTES/DSCOMP.HTM


Mgomes