Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the carrots, parsnips, and sweet potato, then dice them into uniform 1-inch cubes to ensure even roasting.
Place the diced root vegetables and the chicken breast onto the prepared baking sheet.
Drizzle the olive oil over the chicken and vegetables, then sprinkle evenly with dried thyme, rosemary, sea salt, black pepper, and garlic powder.
Toss the vegetables with your hands or tongs to coat thoroughly, and rub the seasoning into both sides of the chicken breast.
Arrange everything in a single layer, ensuring the chicken is in the center and the vegetables are spread out around it.
Roast for 25 to 30 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 it juicy.
Serve the sliced chicken alongside the roasted root vegetables while warm.