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 uniform 1-inch pieces to ensure even cooking.
Mince the garlic cloves and finely chop the fresh rosemary leaves.
In a large mixing bowl, combine the chicken breast, chopped carrots, and parsnips.
Drizzle with extra virgin olive oil and add the minced garlic, rosemary, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are well-coated in the oil and aromatics.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the chicken pieces are not crowded by the vegetables.
Roast in the center of 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 golden.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy.
Plate the sliced chicken alongside the roasted vegetables and serve immediately.