Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel and slice 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 mixing bowl, combine the chicken breast, chopped vegetables, olive oil, minced garlic, herbs, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the oil and herb mixture.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the chicken has enough space to roast evenly.
Place the tray in the oven and roast for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and golden.
Remove from the oven and let the chicken rest for 5 minutes before slicing and serving alongside the roasted root vegetables.