Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Prepare the vegetables by trimming the ends off the Brussels sprouts and slicing them in half; peel the carrots and cut them into 1/2-inch thick rounds.
Place the chicken breast on one side of the baking sheet and arrange the prepared Brussels sprouts and carrots on the other side in a single layer.
Drizzle the olive oil evenly over the chicken and the vegetables.
Sprinkle the rosemary, thyme, garlic powder, sea salt, and black pepper over everything.
Toss the vegetables with your hands or tongs to ensure they are well-coated, and rub the seasoning into both sides of the chicken breast.
Roast in the center of the oven for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with golden-brown edges.
Remove from the oven and let the chicken rest for 5 minutes before slicing against the grain to maintain juiciness.
Plate the sliced chicken alongside the roasted vegetables and serve immediately.