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 for even roasting.
Mince the garlic cloves and finely chop the fresh rosemary and thyme leaves.
In a mixing bowl, toss the chopped root vegetables with half of the olive oil, half of the minced garlic, and a pinch of salt and pepper.
Place the chicken breast on the baking sheet and rub both sides with the remaining olive oil, garlic, rosemary, thyme, salt, and pepper.
Spread the seasoned vegetables in a single layer around the chicken on the baking sheet, ensuring they aren't overcrowded.
Roast for 25-30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and golden-brown.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy, then serve immediately with the vegetables.