Preheat the oven to 400°F (200°C).
Prepare the Brussels sprouts by trimming and halving them.
In a large bowl, combine the halved Brussels sprouts, olive oil, minced garlic, salt, and pepper.
Spread the Brussels sprouts evenly on a baking sheet.
Roast in the oven for 20-25 minutes, stirring halfway through.
Remove from the oven and immediately sprinkle with grated Parmesan cheese.
Return the baking sheet to the oven for an additional 5 minutes, until the cheese is melted and slightly golden.
Drizzle with balsamic vinegar if desired and serve warm.