Fire up your grill for medium-high cooking and prepare a rotisserie basket setup.
Add fries to the basket and close. Turn on the rotisserie and close the lid. Let cook for 20 minutes then check for crispness. If the fries turn golden brown with a bit of char along the edges, they're done! If not, close the lid and cook another 10-25 minutes, checking every 10 minutes or so.
Use heat-proof gloves to remove and open the rotisserie basket. Serve.