Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel and slice the carrots and parsnips into 1/2-inch thick rounds, ensuring they are uniform for even cooking.
Mince the garlic cloves and place them in a large mixing bowl with the olive oil, rosemary, thyme, salt, and pepper.
Pat the chicken breast dry with a paper towel and cut into 1-inch cubes.
Add the chicken, carrots, and parsnips to the bowl and toss thoroughly until every piece is coated in the herb oil.
Spread the mixture in a single layer on the prepared baking sheet, ensuring no pieces are overlapping.
Roast for 20-25 minutes, or until the chicken is cooked through and the vegetables are tender and slightly caramelized.
Remove from the oven and let rest for 5 minutes before serving to allow the juices to redistribute.