1. Preheat your oven to 400°F (200°C).
2. In a large bowl, toss Brussels sprouts with olive oil, salt, and pepper.
3. Spread the Brussels sprouts in a single layer on a baking sheet.
4. Roast for 20-25 minutes, shaking the pan halfway through, until crispy and golden brown.
5. While the Brussels sprouts are roasting, melt the butter and sauté garlic in a skillet for 1-2 minutes until fragrant.
6. Remove the Brussels sprouts from the oven and toss them in the garlic butter sauce.
7. Sprinkle with Parmesan cheese and return to the oven for an additional 5 minutes to melt the cheese.
8. Drizzle with balsamic vinegar (optional) and garnish with chopped parsley before serving.