public void roll(int dimensionX, int dimensionY) {
	      Map<String, Object> parameters = new HashMap<String, Object>();
	      parameters.put("dx", dimensionX);
	      parameters.put("dy", dimensionY);
	      mExecuteMethod.execute("roll", parameters);
	}
Track-ball on android devices can execute roll and press (second currently not implemented) events.
Should be used with lists for precise scrolling (for less precise scrolling swiping can be used).
selendroid-client/src/main/java/io/selendroid/client/TrackBall.java