Preheat oven to 400°F and line a large baking sheet with parchment paper.
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 large mixing bowl, toss the chicken breast, potatoes, and asparagus with the olive oil, minced garlic, rosemary, sea salt, and black pepper until well coated.
Spread the chicken and potatoes onto the prepared baking sheet in a single layer, leaving space for the asparagus later.
Roast the chicken and potatoes for 10 minutes in the preheated oven.
Add the asparagus to the baking sheet and squeeze the juice of the half lemon over all the ingredients.
Continue roasting for 12 to 15 minutes or until the chicken reaches an internal temperature of 165°F and the potatoes are fork-tender.
Allow the chicken to rest for 5 minutes before slicing to ensure it stays juicy.