Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Trim the woody ends off the Brussels sprouts and slice them in half vertically.
Cut the chicken breast into 1-inch bite-sized cubes to ensure even cooking.
In a large mixing bowl, combine the chicken, Brussels sprouts, olive oil, sea salt, black pepper, garlic powder, and chopped rosemary.
Toss everything together until the chicken and vegetables are thoroughly and evenly coated with the oil and seasonings.
Spread the mixture onto the prepared baking sheet in a single layer, turning the Brussels sprouts cut-side down to encourage deep browning.
Roast for 20 to 25 minutes, or until the chicken is cooked through and the sprouts are tender with charred, crispy edges.
Remove from the oven and immediately drizzle the balsamic glaze over the hot chicken and sprouts before serving.