Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Wash and dice the sweet potato into 1/2-inch cubes and trim the woody ends off the asparagus spears.
Mince the garlic clove and zest half of the lemon, then squeeze the juice from the entire lemon into a small mixing bowl.
Whisk the lemon juice, lemon zest, minced garlic, olive oil, dried oregano, sea salt, and black pepper together to create the marinade.
Place the chicken breast, cubed sweet potatoes, and asparagus on the prepared sheet pan in a single layer.
Drizzle the lemon-herb marinade over the chicken and vegetables, tossing the vegetables gently to ensure they are evenly coated.
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 sweet potatoes are tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep the meat juicy and flavorful.