Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Wash and halve the baby potatoes, then trim the tough, woody ends off the asparagus spears.
In a medium bowl, toss the halved potatoes with half of the olive oil, a pinch of sea salt, and black pepper.
Spread the potatoes onto the prepared baking sheet and roast for 12 minutes to give them a head start.
While potatoes roast, mince the garlic and finely chop the fresh rosemary.
Rub the chicken breast with the remaining olive oil, minced garlic, rosemary, salt, and pepper.
Remove the pan from the oven, push the potatoes to one side, and add the chicken breast and asparagus.
Squeeze the juice from the lemon over the chicken and vegetables, placing the spent lemon half on the tray for extra aroma.
Return the pan to the oven and roast for 15 to 18 minutes, or until the chicken reaches an internal temperature of 165°F.
Let the chicken rest for 5 minutes before slicing to ensure it stays juicy and tender.