Preheat the oven to 400°F (207°C). Rinse the Brussels sprouts with water and slice them in half. Heat a skillet (preferably cast-iron) over medium heat. Once heated, add the olive oil. Sauté the garlic briefly, then add the Brussels sprouts, garlic powder, salt, and black pepper. Stir to combine well.
Top the Brussels sprouts with Parmesan cheese and roast in the oven for 8 to 10 minutes. Remove from the oven and serve immediately.