Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Halve the baby potatoes and trim the woody ends off the asparagus spears.
Mince the garlic cloves and finely chop the fresh rosemary leaves.
In a bowl, toss the baby potatoes with half of the olive oil, sea salt, and black pepper.
Spread the potatoes on the baking sheet and roast for 10 minutes.
While potatoes roast, rub the chicken breast with the remaining olive oil, minced garlic, rosemary, and lemon zest.
Move the potatoes to one side of the pan, then add the chicken breast and asparagus to the other side.
Squeeze the juice from the lemon over the chicken and asparagus, then place the remaining lemon slices on top of the chicken.
Roast for another 15-20 minutes until the chicken reaches an internal temperature of 165°F and the potatoes are golden and crisp.