Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper.
Peel the sweet potato and carrots, then dice them into uniform 1-inch cubes for even roasting.
Mince the garlic cloves and finely chop the fresh rosemary leaves.
Place the chicken breast, diced sweet potatoes, and carrots onto the prepared sheet pan.
Drizzle everything with olive oil and sprinkle with the minced garlic, rosemary, sea salt, and black pepper.
Toss the ingredients thoroughly with your hands or tongs to ensure an even coating of oil and seasoning.
Spread the chicken and vegetables out into a single layer, ensuring they are not overcrowded so they roast rather than steam.
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 and golden brown.
Let the chicken rest for 5 minutes before slicing to keep it juicy, then serve alongside the roasted root vegetables.