Preheat oven to 400 degrees f.
Trim and halve the Brussels sprouts, and place in a large glass bowl.
Add the oil and grated Parmesan, and sea salt.
Toss well to coat well, then place everything on a large, rimmed baking tray.
Distribute sprouts evenly in a single layer on the tray.
Roast in your preheated oven for 15-20 minutes, turning once in the middle of roasting time, until golden brown with crunchy outer shells, and the center of the sprouts are tender-crisp.