Disclaimer: I don't have a Drumulator.
I believe they are 8-bit PCM mu-law (μ-255) companded format.
ROM 1: Ride/Cymbal
ROM 2: Mid Tom, Low Tom
ROM 3: Open Hi-Hat, Closed Hi-Hat, Snare, Clave
ROM 4: High Tom, Kick, Rimshot, Clap, Cowbell
You can probably use the same utilities for WAV/BIN manipulation as the Oberheim DMX.