Place the prepared Brussels sprouts in a large bowl. Drizzle with olive oil. Add the garlic cloves, salt, and pepper. Stir with a spoon to mix. Evenly spread out the Brussels sprouts in a single layer on a sheet pan. Roast for 20-30 minutes, until tender and browned. Turn once during the roasting process.
Remove from the oven and drizzle with the balsamic vinegar and toss again. Plate, then garnish with Parmesan cheese.