Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the carrots and slice them into half-inch rounds, and cut the red onion into bite-sized wedges.
Place the chicken breast, broccoli florets, sliced carrots, and onion wedges onto the prepared baking sheet in a single layer.
Drizzle the olive oil over the chicken and all of the vegetables.
Evenly sprinkle the dried rosemary, dried thyme, garlic powder, sea salt, and black pepper over the entire tray.
Toss the vegetables with your hands or tongs to ensure they are well-coated in the oil and spices, then flip the chicken to season both sides.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing it against the grain and serving alongside the roasted vegetables.