Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel and slice the carrots and parsnips into half-inch rounds, and cut the red onion into thick wedges.
In a large bowl, toss the sliced carrots, parsnips, and onions with half of the olive oil, half of the sea salt, and half of the black pepper.
Spread the vegetables in a single layer on the prepared baking sheet and roast for 15 minutes.
While vegetables roast, mince the garlic and finely chop the fresh rosemary and thyme.
Pat the chicken breast dry and rub with the remaining olive oil, minced garlic, rosemary, thyme, salt, and pepper.
Remove the baking sheet from the oven, toss the vegetables, and place the seasoned chicken breast in the center of the pan.
Return the pan to the oven and roast for an additional 18-22 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are golden brown.
Remove from the oven and let the chicken rest for 5 minutes before slicing to ensure the juices redistribute.
Plate the sliced chicken alongside the roasted root vegetables and serve immediately.