Move the oven rack to the upper-middle position and preheat to 500 degrees F. In a large bowl toss together the Brussels sprouts, olive oil, water, balsamic vinegar, salt, and pepper until well coated.
Line a rimmed baking sheet with foil and place the sprouts cut side down. Cover the baking sheet with another piece of foil and roast the sprouts for 12 minutes. Then, remove the foil and keep cooking for another 12-14 minutes, or until the sprouts are browned and tender.
Season the Brussels sprouts with salt and pepper to taste and serve.
Select sprouts that are about 1½ inches long. Quarter Brussels sprouts longer than 2½ inches; don’t cut sprouts shorter than 1 inch.