The rotation itself is done by setting the value of the "theRot" event out. The value is an axis and an absolute angle. the VRML spec the axes are x (to the right), y (up) and z (towards viewer shooting out of the screen).
When the setValue is called this generates an event. Recall, this was routed to the set_rotation call on the cone.
There are other ways of doing rotations using the Java API provided by Community Place. We shall see these in more advanced tutorials.