Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper.
Peel and slice the carrots and parsnips into 1/2-inch thick rounds, and cut the red onion into small wedges.
Mince the garlic cloves and finely chop the fresh rosemary and thyme leaves.
In a large mixing bowl, toss the sliced carrots, parsnips, and onions with half of the olive oil, half of the garlic, and a pinch of salt and pepper.
Spread the vegetables in a single layer on the prepared sheet pan, leaving space in the center for the chicken.
Rub the chicken breast with the remaining olive oil, garlic, rosemary, thyme, sea salt, and black pepper until evenly coated.
Place the chicken breast in the center of the sheet pan surrounded by the vegetables.
Roast in the oven for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and slightly caramelized.
Remove from the oven and let the chicken rest for 5 minutes before slicing to ensure it stays juicy.
Serve the sliced chicken alongside the roasted root vegetables.