Preheat your oven to 425°F.
In a small bowl, mix the olive oil, lemon juice (squeezed from the medium lemon), rosemary, thyme, garlic powder, salt, and pepper.
Place the chicken breast in a shallow dish and coat it evenly with the lemon herb mixture. Allow it to marinate for at least 10 minutes.
Meanwhile, peel (if desired) and chop the sweet potato into evenly sized cubes. Trim the asparagus ends.
On a baking sheet, toss the sweet potatoes and asparagus with a light drizzle of olive oil, salt, and pepper.
Place the marinated chicken on another baking tray or alongside the vegetables if space allows.
Roast the vegetables in the oven for 20-25 minutes until they are tender and lightly browned.
Bake the chicken for 18-20 minutes or until it reaches an internal temperature of 165°F. For extra crispiness, you can broil the chicken for an additional 2-3 minutes at the end.
Plate the chicken with a serving of roasted sweet potatoes and asparagus. Garnish with extra lemon wedges if desired and serve warm.