Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper.
Wash and halve the baby potatoes, then toss them directly on the pan with 0.5 tablespoons of olive oil and a pinch of sea salt.
Spread the potatoes in a single layer and roast for 10 minutes to give them a head start.
While potatoes roast, whisk together the remaining olive oil, lemon juice, lemon zest, minced garlic, and dried rosemary in a small bowl.
Season the chicken breast with the remaining sea salt and black pepper, then brush it generously with half of the lemon-herb mixture.
Remove the pan from the oven, push the potatoes to one side, and place the chicken breast and trimmed asparagus spears on the empty space.
Drizzle the remaining lemon-herb mixture over the asparagus and toss lightly to coat.
Return the pan to the oven and roast for another 15 to 20 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are golden.