Input: yellow shaft.
Blue shaft receives rotary motion from the input through helical gear.
The blue shaft has prismatic joint (sliding key) with green gear.
Turn violet screw for moving orange slider to adjust relative positioning angle between yellow and blue rollers thanks to the helical teeth. In this animation the yellow shaft is supposedly kept immobile.
The adjustment can be performed even during transmission.
The self-locking of the violet screw preserves the adjusted angle from accidental motion of the green gear.
For larger angular adjustment use smaller gears and add intermediate gears to keep roller center distance unchanged.
STEP files of this video:
Inventor files: