In a large mixing bowl, combine the halved Brussels sprouts with the olive oil, minced garlic, garlic powder, black pepper, sea salt, and red pepper flakes (if using). Toss until the Brussels sprouts are evenly coated.
Spread the Brussels sprouts in a single layer on a baking sheet lined with parchment paper.
Roast in the preheated oven for 20-25 minutes, or until the Brussels sprouts are golden brown and crispy on the outside, stirring halfway through for even cooking.
Remove from the oven and immediately sprinkle the grated Parmesan cheese over the hot Brussels sprouts. Return to the oven for an additional 3-5 minutes to allow the cheese to melt and become bubbly.
Once done, remove from the oven and garnish with fresh chopped parsley before serving.