The U-110 uses PCM samples in ROM, largely derived from the samples used for the S-series of samplers, such as the S-330, S-550, S-10, MKS-10, W-30 and so forth.

The structure of this module is basic, and it focuses solely on providing samples of acoustic/electric instruments used in pop/rock.  There are no filters or deep editing possibilities, and no reverb/delay effects on board - for that, users had to wait until the successor Roland U-220 was produced.  There are chorus and tremolo effects though.
 

One point in which the U-110 is superior to the U-220 is the addition of four slots for the SN-U110-series of cards.  These can all be used at the same time.  The U-20/220 only had two of these slots.

The sounds are classic Roland, and even if they now sound dated, it's interesting to see what sounds the designers chose to put in ROM:  there are only pop/rock sounds, and even in the rhythm set, there are no sign of the TR-808 or 909 samples that would become so important just the year after this module was released.

Interesting to note also that the different DACs and lack of internal reverb do not detract from the U-110 sound:  on the other hand, the U-110 comes through as powerful, full of character, and with a sort of "presence" in its sonic aspect, that I can say this has more of a "raw", in your face quality than its successor U-220, which is more polished, refined but maybe not as "vibey" ;-)

Turning the unit on while pressing "DEC" and "INC" simultaneously, you enter test mode:  on my unit, the display shows "U-110  Ver2.03".

Initialize the Roland U-110:  turn on the unit while pressing simultaneously "PART" and "EDIT".