Preheat your oven to 400°F and line a large rimmed sheet pan with parchment paper for easy cleanup.
Prepare the vegetables by peeling and slicing the carrots and parsnips into 1-inch rounds, and cutting the red onion into thick wedges.
In a large mixing bowl, combine the chicken breast, carrots, parsnips, and onion wedges.
Drizzle the olive oil over the chicken and vegetables, then add the minced garlic, chopped rosemary, thyme, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the oil and aromatics.
Spread the mixture in a single layer on the prepared sheet pan, ensuring the chicken breast is in the center and not covered by 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 tender and slightly caramelized.
Remove from the oven and let the chicken rest for 5 minutes before slicing to ensure it stays juicy, then serve immediately with the roasted vegetables.