Take a look at the Jaguar or Victor class. These are used to control a single motor. In fact, RobotDrive by default creates two or four instances of Jaguar.
For example:
Code:
Jaguar motor = new Jaguar(5); // Motor connected to Jaguar on PWM #5
Joystick stick = new Joystick(2);
// operator control:
motor.set(stick.getY()); // set the motor output to Y-axis input on Joystick #2