While air fryer preheats, slice brussels sprouts in half and add to a bowl. Add olive oil, salt, pepper, and a pinch of red pepper flakes (if using). Stir to coat brussels sprouts in oil and seasonings.
Place parchment paper in the air fryer basket (this will keep the parmesan cheese from falling through the grates in the air fryer). Then add the brussels sprouts to the air fryer.
Air fry at 380 degrees for 10 minutes, then stir.
While brussels sprouts cook, grate your parmesan cheese if using fresh parmesan cheese.
After brussels sprouts have cooked for 10 minutes, open air fryer, stir brussels sprouts, then top with parmesan cheese.
Close air fryer and cook for an additional 4-5 minutes at 380 degrees F.
Plate and enjoy.
Notes
Watch brussels sprouts carefully to make sure they get roasted but not burned.
If you have larger brussels sprouts, you may need to cut them in quarters instead of halves.
All air fryers cook differently. Adjust cook times as needed.