Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper.
Peel the carrots and parsnips, then chop them along with the red onion into uniform 1-inch chunks.
Finely mince the garlic clove and roughly chop the fresh rosemary and thyme leaves.
In a large mixing bowl, toss the chopped vegetables with half of the olive oil, half of the minced herbs, and a pinch of the salt and pepper.
Pat the chicken breast dry with a paper towel and rub it thoroughly with the remaining olive oil, herbs, salt, and pepper.
Spread the seasoned vegetables in a single layer across the prepared sheet pan, leaving space in the middle.
Place the chicken breast in the center of the pan, nestling it slightly among the root vegetables.
Roast in the oven for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and slightly caramelized.
Remove from the oven and let the chicken rest for 5 minutes before slicing to ensure the juices stay locked in.