Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Pat the chicken breast completely dry with paper towels and season both sides with half of the sea salt and black pepper.
Peel and chop the carrots and parsnips into one-inch chunks, and slice the red onion into thick wedges.
In a large mixing bowl, combine the chopped vegetables with olive oil, minced garlic, dried rosemary, dried thyme, and the remaining sea salt and pepper.
Toss the vegetables until they are thoroughly and evenly coated with the oil and herb mixture.
Spread the vegetables in a single layer on the prepared baking sheet, leaving an open space in the center.
Place the seasoned chicken breast in the center of the baking sheet 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 root vegetables are fork-tender and golden.
Remove from the oven and let the chicken rest for 5 minutes to lock in the juices before slicing.
Serve the sliced chicken alongside the roasted vegetables, drizzling any remaining pan juices over the top.