Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Wash and peel the sweet potato, then dice it into uniform 1/2-inch cubes; trim the woody ends off the asparagus spears.
Place the chicken breast, sweet potato cubes, and asparagus onto the prepared baking sheet in a single layer.
Drizzle the olive oil over the chicken and vegetables, then squeeze the juice from the lemon half over everything.
Evenly sprinkle the dried rosemary, garlic powder, sea salt, and black pepper over the chicken and produce.
Toss the vegetables with tongs to ensure they are well-coated in oil and spices, and flip the chicken to season both sides.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are fork-tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy, then serve immediately.