Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Peel the carrots and parsnips, then chop them into uniform 1-inch coins; slice the red onion into thick wedges.
In a large mixing bowl, toss the chopped vegetables with half of the olive oil, minced garlic, and half of the fresh herbs.
Place the chicken breast on the prepared baking sheet and rub both sides with the remaining olive oil, rosemary, thyme, salt, and pepper.
Spread the seasoned vegetables in a single layer around the chicken, ensuring they aren't overcrowded so they can caramelize properly.
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 vegetables are fork-tender.
Remove from the oven and let the chicken rest for 5 minutes to lock in the juices before slicing and serving.