Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet 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, combine the chicken breast, sliced carrots, parsnips, and onions.
Drizzle the olive oil over the mixture and add the minced garlic, rosemary, thyme, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the oil and herbs.
Spread the mixture onto the prepared baking sheet in a single layer, ensuring the chicken has space around it to brown.
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 fork-tender.
Remove from the oven and let the chicken rest for 5 minutes to lock in the juices before slicing.
Plate the sliced chicken alongside the roasted root vegetables and serve immediately.