Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Peel and chop the carrots and parsnips into 1-inch chunks, and slice the red onion into thick wedges.
Mince the garlic cloves finely.
In a large mixing bowl, combine the chicken breast, chopped carrots, parsnips, and red onion.
Drizzle with extra virgin olive oil and sprinkle with minced garlic, dried thyme, dried rosemary, sea salt, and black pepper.
Toss everything thoroughly to ensure the chicken and vegetables are evenly coated in the oil and seasonings.
Spread the mixture onto the prepared baking sheet in a single layer, ensuring the chicken is not covered 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 golden-brown.
Remove from the oven and let the chicken rest for 5 minutes before slicing.
Serve the sliced chicken alongside the roasted root vegetables.