Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Peel and chop the carrots and parsnips into 1-inch chunks, and halve the Brussels sprouts.
Mince the garlic cloves and finely chop the fresh rosemary and thyme leaves.
In a large bowl, toss the prepared vegetables with half of the olive oil, half of the minced garlic, and a pinch of the sea salt and black pepper.
Place the chicken breast on the prepared sheet pan and rub with the remaining olive oil, garlic, rosemary, thyme, salt, and pepper.
Spread the seasoned vegetables in a single layer around the chicken on the sheet pan, ensuring they aren't overcrowded.
Roast for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are fork-tender and lightly browned.
Let the chicken rest for 5 minutes before slicing to keep it juicy, then serve alongside the roasted root vegetables.