Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel the sweet potato and carrots, then chop them into 1-inch cubes; slice the red onion into thick wedges.
Place the chicken breast and the chopped vegetables onto the prepared baking sheet in a single layer.
Drizzle the olive oil over the chicken and vegetables, ensuring everything is lightly coated.
Evenly sprinkle the dried rosemary, thyme, garlic powder, sea salt, and black pepper over all ingredients.
Toss the vegetables with your hands or a spatula to distribute the seasoning, and rub the herbs into both sides of the chicken.
Roast in the center of the oven for 25 to 30 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 to ensure it remains juicy.