Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast and the peeled sweet potato into uniform 1-inch cubes to ensure even cooking.
Trim the woody ends off the asparagus and cut the stalks into 2-inch pieces.
In a large mixing bowl, combine the chicken, sweet potato, and asparagus with the olive oil, dried oregano, garlic powder, sea salt, and black pepper.
Toss everything thoroughly until the ingredients are well-coated in the oil and spices.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the pieces aren't overcrowded so they roast rather than steam.
Roast for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the sweet potatoes are fork-tender and slightly caramelized.
Remove from the oven and immediately drizzle with fresh lemon juice and sprinkle with lemon zest for a bright, citrusy finish.