Preheat the oven to 425°F (220°C).
Trim the stem ends from the Brussels sprouts and cut any large sprouts in half lengthwise; leave small ones whole.
In a large bowl, toss the Brussels sprouts with 1 1/2 tablespoons extra virgin olive oil, 1/2 teaspoon salt, 1/4 teaspoon freshly ground black pepper, and a pinch of crushed red pepper flakes if using, until evenly coated.
Arrange the sprouts in a single layer on a rimmed baking sheet, cut-side down if halved.
Roast for 20 minutes, stirring or flipping once after about 10 minutes, until tender and browned.
While the sprouts roast, whisk together the remaining 1 tablespoon extra virgin olive oil, 1 tablespoon balsamic vinegar, and 1 teaspoon honey in a small bowl.
Transfer the roasted Brussels sprouts to a serving bowl, pour the balsamic-honey mixture over them, toss to coat, and serve hot.