Preheat oven to 400 degrees f.
Trim and halve the Brussels sprouts, then place on a large baking tray.
Add the oil and grated Parmesan.
Toss to coat well.
Distribute sprouts evenly in a single layer on the tray.
Roast in the hot oven for 15-20 minutes, or until golden brown, and the sprouts tender-crisp.