Preheat your oven to 400°F (200°C) and line a large baking sheet 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.
Mince the fresh garlic and finely chop the rosemary and thyme leaves.
In a large mixing bowl, combine the chicken breast, cubed root vegetables, olive oil, minced garlic, herbs, salt, and pepper.
Toss the mixture thoroughly until the chicken and vegetables are well-coated in the herb oil.
Spread the ingredients in a single layer on the prepared baking sheet, making sure not to overcrowd the pan.
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 tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing and serving with the roasted vegetables.