Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Wash the potato and dice it into uniform 1/2-inch cubes to ensure even cooking.
Place the potato cubes on one side of the sheet pan and toss with 0.5 tbsp of olive oil, half of the rosemary, sea salt, and black pepper.
Spread the potatoes in a single layer and roast in the oven for 15 minutes.
While potatoes roast, rub the chicken breast with the remaining 0.5 tbsp of olive oil, garlic powder, the rest of the rosemary, salt, and pepper.
Remove the pan from the oven, move the potatoes to one side, and add the chicken breast and asparagus spears to the empty space.
Return the pan to the oven and roast for an additional 15 to 20 minutes, or until the chicken reaches an internal temperature of 165°F.
Remove from the oven and drizzle the fresh lemon juice over the chicken and asparagus before serving.