Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Wash and halve the baby potatoes, and trim the tough woody ends off the asparagus spears.
Mince the garlic clove and finely chop the fresh rosemary leaves.
In a small bowl, whisk together the olive oil, minced garlic, rosemary, sea salt, and black pepper.
Place the halved potatoes on the baking sheet, drizzle with half of the herb oil mixture, and toss to coat.
Roast the potatoes for 10 minutes to give them a head start.
Remove the sheet from the oven, push the potatoes to one side, and place the chicken breast and asparagus on the other side.
Brush the remaining herb oil over the chicken and asparagus, then top the chicken with thin slices of the lemon.
Return the pan to the oven and roast for 15 to 20 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender.