Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper.
Peel the carrots and parsnips, then chop them into uniform 1-inch rounds or chunks.
Place the chopped vegetables on the prepared baking sheet and toss with half of the olive oil, half of the sea salt, and half of the black pepper.
Mince the garlic cloves and finely chop the fresh rosemary and thyme leaves.
Pat the chicken breast dry with a paper towel and rub with the remaining olive oil, minced garlic, rosemary, and thyme.
Season the chicken with the remaining sea salt and black pepper, then nestle it onto the baking sheet surrounded by the vegetables.
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 it against the grain to serve.