Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the carrots and parsnips, then chop them into 1-inch rounds; peel the red onion and cut into thick wedges.
In a large mixing bowl, toss the prepared vegetables with half of the olive oil, half of the minced garlic, and a pinch of sea salt and pepper.
Spread the vegetables in a single layer across the baking sheet, leaving space in the center for the chicken.
Pat the chicken breast dry with a paper towel and rub both sides with the remaining olive oil, garlic, rosemary, thyme, salt, and pepper.
Place the chicken breast in the center of the baking sheet surrounded by the root vegetables.
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 golden brown.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep the juices intact, then serve immediately with the roasted vegetables.