Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Peel and dice the sweet potato, carrots, and parsnips into uniform 1-inch cubes to ensure they roast evenly.
In a large mixing bowl, whisk together the extra virgin olive oil, minced garlic, rosemary, thyme, salt, and pepper.
Add the diced root vegetables and the chicken breast to the bowl, tossing thoroughly until every piece is well-coated in the herb oil.
Spread the vegetables and chicken in a single layer on the prepared baking sheet, making sure not to overcrowd the pan.
Roast for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are fork-tender and golden.
Allow the chicken to rest for 5 minutes before slicing to retain its juices, then serve alongside the roasted vegetable medley.