Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Peel the carrots and parsnips, then chop them into uniform 1-inch chunks.
Mince the garlic cloves and finely chop the fresh rosemary and thyme leaves.
In a large mixing bowl, combine the chicken breast, chopped root vegetables, olive oil, minced garlic, herbs, salt, and pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the herb oil.
Spread the mixture onto the prepared baking sheet in a single layer, ensuring the chicken pieces are not crowded.
Roast for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are fork-tender and lightly browned.
Remove from the oven and let the chicken rest for 5 minutes before serving to keep it juicy.