Preheat your oven to 400°F.
In a small bowl, whisk together olive oil, juice from 1/4 lemon, minced garlic, dried thyme (if using), salt, and pepper.
Place the chicken breast on one side of a large sheet pan. Brush both sides with half of the lemon-garlic mixture.
Peel and cube the sweet potato into 1/2-inch pieces. Toss with a splash of olive oil, salt, and pepper, and spread on the sheet pan.
Trim the woody ends of the asparagus and lightly coat with the remaining lemon-garlic mixture.
Arrange all items in a single layer on the pan to ensure even cooking.
Roast in the oven for about 25-30 minutes until the chicken reaches an internal temperature of 165°F, the sweet potato cubes are tender and slightly crispy, and the asparagus is fork-tender.
If desired, broil for an additional 2-3 minutes to crisp up the sweet potatoes and asparagus.
Remove from the oven and let rest for a few minutes before serving.