Rotates all sprites on a channel by a relative amount of rotAmount degrees clockwise at a speed of speed degrees per frame. If speed is negative, it is seen as the number of steps to complete the rotation in. If forever is non-zero then the the sprite will continue to rotate in the direction indicated by rotAmount forever.
For example:
"R 90,-10,0"
Means rotate 90 pixels clockwise in 10 steps.
"R -1,10,1"
Means rotate 10 degrees a frame anti-clockwise forever.
"R 720,0.5,0"
Means rotate the sprite 720 degrees (that's 2 complete rotations) clockwise at half a degree a frame.
See also the Rotate Sprite command.