Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Trim the woody ends off the Brussels sprouts and slice them in half; cut the chicken breast into even 1-inch bite-sized pieces.
In a large mixing bowl, combine the chicken and Brussels sprouts with the olive oil, garlic powder, onion powder, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the oil and spices.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the pieces are spread out to allow for even roasting and browning.
Roast for 20 to 25 minutes, tossing the ingredients halfway through, until the chicken is cooked through and the sprouts have developed charred, crispy edges.
Remove from the oven, drizzle the balsamic vinegar over the hot pan, and toss one final time before serving.