Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Scrub the sweet potato and dice it into 1/2-inch cubes, then place them on the sheet pan.
Mince the garlic and finely chop the fresh rosemary and thyme.
Drizzle the sweet potatoes with 0.5 tbsp of olive oil and sprinkle with half of the garlic, herbs, salt, and pepper.
Roast the sweet potatoes for 15 minutes.
While the potatoes roast, pat the chicken breast dry and season both sides with the remaining olive oil, garlic, herbs, salt, and pepper.
Move the potatoes to one side of the pan and add the chicken breast and trimmed asparagus to the other side.
Roast for another 15-20 minutes, or until the chicken reaches an internal temperature of 165°F and the asparagus is tender-crisp.
Squeeze fresh lemon juice over the chicken and vegetables before serving.