Place brussel sprouts, olive oil, garlic lemon juice, lemon rind, salt, and pepper into a large bowl. If you choose to use chili flakes add them in now. Mix well.
Spread the Brussels sprouts mixture on a baking sheet, making sure they are spread evenly to ensure that they cook evenly. Bake for 10 minutes and remove from the oven.
Toss the Brussels sprouts to turn them, ensuring a nice browning all round, and bake for an additional 5–10 minutes or until the sprouts are golden-brown in color.
Remove from oven, toss the Brussels sprouts with the Parmesan cheese, and serve.