How to convert joystick position to rotation?

I have been working through the Penelope script to get my head round linking a GUI joystick to a Game Object. I have a scene setup with a simple cube object driven by the joystick.

The following code works fine and will move the cube around when I move the joystick pad:

 var moveJoystick : joystickControl; //the enumerated joystick pad
 
 var objectTransform : Transform; //a simple cube
 
 function Update()
 {
 var cubeMovement = moveJoystick.position;
 objectTransform.Translate (cubeMovement.x, 0, cubeMovement.y, 0 );
 }

However, as soon as I try something similar using rotation - it has no effect. The cube does not spin/move at all:

 var rotateJoystick : joystickControl; //the enumerated joystick pad
 
 var objectRotate : Transform;    //the simple cube object
 
 var rotationSpeed : Vector2 = Vector2( 50, 25 );
 
 function Update()
 {
 var cubeRotate = rotateJoystick.position; // Scale joystick input with rotation speed
     cubeRotate.x *= rotationSpeed.x;
     cubeRotate.y *= rotationSpeed.y;
     cubeRotate *= Time.deltaTime;
 
 objectRotate.Rotate (cubeRotate.x, cubeRotate.y, 0, 0 );
 }

I tried to reverse engineer the tutorial so I could pull out a better understanding of the principles, however I am clearly missing something fundamental. Could anyone point me in the right direction? I have searched and tried variations on the above rotation code but to no avail. Is it anything to do with euler/quaternion?