Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Peel the carrots and parsnips, then chop them into 1-inch bite-sized pieces. Trim and halve the Brussels sprouts.
Finely mince the garlic cloves.
In a large mixing bowl, combine the chicken breast, chopped carrots, parsnips, and Brussels sprouts.
Drizzle with extra virgin olive oil 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 seasonings.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the chicken has space around it to roast properly.
Bake 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 to keep it juicy.
Serve the sliced chicken alongside the roasted root vegetables.