This post explains how to make realistic sounding drum rolls with a drum machine. In order to sound like a drummer, you need to think like one. Firstly, I need to define, for those non-drummers, that there are two main types of rolls:
- The single-stroke roll: The hand pattern is Right (R), Left (L), Right, Left...and the sticks do not bounce at all. Often heard in Nirvana's songs.
- The multiple-bounce roll: The hand pattern is R,L,R, L...and the sticks bounce several times with each stroke. Often heard at the circus before anything "exciting"* happens. It is also often heard in songs played by any half-decent drummer.
* Exciting is in inverted commas because I don't believe much exciting happens at the circus :-)
With that in mind, we can edit the volume of each hit to mimic the movements of the drummers arms. Every drummer has a weaker arm, which will produce a quieter and different sounding hit. It produces a different sound because it has to hit the drum head at a different point to that of the other hand. The easiest way to mimic this with a drum machine is to make the each weaker hand's hit about 1/2 to 3/4 the volume of the stronger hand's. Being a right-handed drummer, I always choose the left hand to be weaker. This means that a single-strike roll will look like the figure below in Hydrogen:

For the multiple-bounce roll, one needs to make the sticks sound like they are bouncing. The first way to do this can be really painstaking and yields rather poor results. For this method, you add each bounce sound in as a snare hit but with a much quieter volume. This is seen below:

A better sounding and easier way of doing this is to use a drumkit which has a drag/ghost note prerecorded (A drag is a drum note which lets the drumstick bounce). The hydrogen kit that I made (available
here) has a drag note and produces a simpler multiple-bounce roll seen below.

Here is and mp3 of each of the above rolls:
Rolls.mp3 (285 kB). The first roll is a single-stroke roll followed by the two multiple-bounce rolls, the first is uses no drag/ghost hits and the second does.
These are the easiest ways of getting realistic drum rolls out of a machine. Bare in mind that a machine will never sound exactly like a drummer, there are just too many variables. Hydrogen also has a cool
humanize dial which makes each beat slightly out of time randomly. This can be useful, but don't overdo it.
Other posts you might find interesting:
How to make a Hydrogen DrumkitPimp my BeatsMultiple Outputs for HydrogenMy Attempt at a Hydrogen DrumkitHydrogen Drumkits