Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Peel the carrots and parsnips, then slice them into 1-inch rounds; cut the red onion into thick wedges.
In a large mixing bowl, combine the chicken breast and the prepared vegetables.
Drizzle with olive oil and add the minced garlic, rosemary, thyme, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the oil and herbs.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the chicken is not covered by the vegetables.
Roast for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the root vegetables are tender and lightly caramelized.
Remove from the oven and let the chicken rest for 5 minutes before slicing and serving alongside the roasted vegetables.