Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Peel the carrots and parsnips, then chop them into uniform 1-inch chunks to ensure even cooking.
Mince the garlic cloves and finely chop the fresh thyme and rosemary leaves.
In a large mixing bowl, combine the chicken breast, chopped root vegetables, olive oil, minced garlic, herbs, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are well-coated in the oil and seasonings.
Spread the mixture onto the prepared baking sheet in a single layer, ensuring the chicken is not covered by the vegetables.
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 and lightly browned.
Remove from the oven and let the chicken rest for 5 minutes before slicing to ensure the juices stay locked in.