Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Peel and slice the carrots into half-moons, cube the parsnips, and cut the red onion into thick wedges.
Place the chicken breast and chopped vegetables onto the prepared baking sheet.
In a small bowl, whisk together the olive oil, minced garlic, rosemary, thyme, sea salt, and black pepper.
Pour the herb oil over the chicken and vegetables, tossing thoroughly to ensure every piece is well-coated.
Spread everything in a single layer, ensuring the chicken is not crowded by the vegetables so it roasts evenly.
Roast for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are fork-tender.
Let the chicken rest for 5 minutes before slicing to maintain its moisture.