Hmmm...I haven't heard the roland patch, but my gut instinct is that you better check your equipment. Are you using an amp? Active monitors? Headphones? Is there something in between like a mixer? A lot of cheap equipment will negate the money you spent on the sampler. Cheap equipment will filter out highs and lows (especially lows).

If you still can't hear the subtle differences (hammer action, bass resonance) you may consider getting your hearing tested. If you have gone to lots of rock concerts or played in bands, you're in a high risk group to lose your hearing and you'll lose the highs and lows first...another source of filtering.