Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the carrots and parsnips, then chop them into 1-inch chunks, and slice the red onion into thick wedges.
Mince the garlic cloves and finely chop the fresh rosemary and thyme leaves.
In a large mixing bowl, toss the prepared carrots, parsnips, and onions with half of the olive oil, half of the minced garlic, and half of the salt and pepper.
Pat the chicken breast dry with a paper towel and rub it thoroughly with the remaining olive oil, garlic, rosemary, thyme, salt, and pepper.
Spread the seasoned vegetables in a single layer on the baking sheet and nestle the chicken breast in the center of the pan.
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 and caramelized.
Remove from the oven and let the chicken rest for 5 minutes before slicing to ensure it stays incredibly juicy.