Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Trim the Brussels sprouts and cut them in half; peel and slice the carrots into rounds, and cut the red onion into small wedges.
Place the chicken breast and all the prepared vegetables onto the baking sheet.
Drizzle everything with olive oil and sprinkle evenly with dried rosemary, dried thyme, garlic powder, sea salt, and black pepper.
Toss the vegetables to coat thoroughly and ensure the chicken is well-seasoned on both sides.
Arrange the chicken in the center with the vegetables spread out in a single layer around it.
Roast for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and browned.
Let the chicken rest for 5 minutes before slicing and serving with the roasted vegetables.