The quality is really good - just add effects and proper playing technique to obtain excellent results in your arrangements.

This library focuses on the main ingredient of the groove, drums and bass.  There are so many drum kit variations that it would be hard for anybody not to find what they're looking for.

For the guitar/bass section, there's plenty to choose - although not as much as the drums - but all the "usual suspects" are there, including incredible Fender guitars and basses, acoustics, fretless, even some synth bass.
 

The quality of these samples is - as you can hear below - very high.  All Roland sample-based synths and modules, more or less, were built upon these samples, and you can definitely recognize many samples that are contained in the JV/XP series.  Of course, having the luxury of up to 32MB of sounds playing at the same time, the quality if higher than those.

In order to use these CD-ROMs you will need a SCSI CD-ROM drive connected to your S-series sampler or XV-5080.  Keep in mind that certain sound data will need 32MB of memory, supported only by the S-760.  The S-770 and 750 have less.