Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel the carrots and parsnips, then chop them into 1-inch chunks. Trim and halve the Brussels sprouts.
Mince the garlic clove finely.
In a large mixing bowl, combine the chopped vegetables with half of the olive oil, half of the rosemary, half of the thyme, and a pinch of salt and pepper.
Place the chicken breast on the prepared baking sheet and rub with the remaining olive oil, minced garlic, and the rest of the herbs and seasoning.
Arrange the seasoned vegetables in a single layer around the chicken on the baking sheet.
Roast in the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and lightly browned.
Remove from the oven and let the chicken rest for 5 minutes before slicing it against the grain to serve with the roasted vegetables.