Preheat your oven to 400°F and line a large sheet pan with parchment paper.
Wash and peel the sweet potato, then cut it into 1-inch cubes. Trim the woody ends off the asparagus spears.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, chopped rosemary, sea salt, and black pepper.
Place the chicken breast and sweet potato cubes on the prepared sheet pan, then drizzle with three-quarters of the lemon-herb mixture, tossing to coat evenly.
Roast in the oven for 15 minutes.
Remove the pan from the oven, add the asparagus spears to the empty space, and drizzle them with the remaining lemon-herb mixture.
Return the pan to the oven and roast for an additional 10 to 12 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender.
Let the chicken rest for 5 minutes before slicing and serving alongside the roasted vegetables.