Preheat the oven to 425°F (220°C). Line a baking sheet with parchment for easy cleanup.
Trim the stem ends of the Brussels sprouts and cut them in half. Pat completely dry with a towel.
In a large bowl, toss the sprouts with olive oil and a generous pinch of salt and black pepper until evenly coated.
Spread the sprouts in a single layer, cut-side down, on the prepared baking sheet and avoid overcrowding.
Roasting and Glazing
Roast for 20–25 minutes, turning once halfway, until the cut sides are deeply golden and the outer leaves are crisped.
Meanwhile, combine balsamic vinegar and honey in a small saucepan. Whisk in Dijon if using, and bring to a low simmer over medium heat.
Cook for 2–3 minutes until slightly thickened. Remove from heat and stir in minced garlic if desired.
Transfer the roasted sprouts to a large bowl, pour the warm glaze over them, and toss quickly to coat.
Serving
Serve hot with a light sprinkle of red pepper flakes if desired.
Notes
Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in a 400°F (200°C) oven for best texture. To freeze, flash-freeze on a tray and transfer to a freezer bag. Thaw and re-crisp in the oven.