Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Halve the baby potatoes and place them on one side of the pan, tossing them with 0.25 tablespoons of the olive oil and a pinch of the sea salt and black pepper.
Roast the potatoes alone for 10 minutes to ensure they become tender and golden.
While potatoes roast, pat the chicken breast dry with a paper towel and trim the woody ends off the asparagus spears.
In a small bowl, whisk together the remaining 0.5 tablespoons of olive oil, lemon juice, lemon zest, minced garlic, and dried rosemary.
Remove the pan from the oven and place the chicken breast and asparagus in the remaining space.
Drizzle the lemon-herb mixture evenly over the chicken and asparagus, then sprinkle the remaining salt and pepper over everything.
Return the pan to the oven and roast for 15-20 minutes, or until the chicken reaches an internal temperature of 165°F and the asparagus is tender-crisp.
Allow the chicken to rest for 5 minutes before slicing against the grain to maintain maximum juiciness.