Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Peel the carrots and parsnips, then slice them into uniform 1/2-inch thick rounds to ensure even cooking.
Mince the garlic cloves finely and place them in a small bowl with the olive oil, rosemary, thyme, salt, and pepper.
Place the chicken breast and the sliced root vegetables on the prepared sheet pan.
Drizzle the garlic-herb oil over the chicken and vegetables, using your hands or a brush to coat everything thoroughly.
Arrange the ingredients in a single layer, ensuring the chicken is not covered by the vegetables.
Roast in the center of the oven for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are fork-tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy.
Serve the sliced chicken alongside the roasted root vegetables while warm.