Begin by preheating your oven to 400°F (200°C) to ensure it's hot enough for roasting.
In a large mixing bowl, toss together the halved Brussels sprouts, minced garlic, olive oil, and red pepper flakes (if you desire a little heat). Season generously with salt and pepper, mixing until each Brussels sprout is well-coated in the flavorful mixture.
Arrange the Brussels sprouts on a baking sheet, ensuring they're spread out in a single layer with the cut sides facing down.
Place the baking sheet in the preheated oven and roast for 20-25 minutes, stirring halfway through to ensure even cooking.
When the Brussels sprouts are tender with crispy edges and a golden hue, take the baking sheet out of the oven. Immediately sprinkle the freshly grated Parmesan cheese over the hot Brussels sprouts.
Return the baking sheet to the oven for another 5 minutes, or until the cheese is melted and slightly crispy.
Once done, remove from the oven and let the Brussels sprouts cool for a moment. Just before serving, garnish with finely chopped fresh parsley.