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 the sheet pan, tossing with half of the olive oil, the dried rosemary, salt, and pepper.
Roast the potatoes in the oven for 15 minutes to give them a head start.
While the potatoes roast, whisk together the remaining olive oil, lemon juice, lemon zest, dried thyme, and minced garlic in a small bowl.
Pat the chicken breast dry with a paper towel and brush both sides with half of the prepared lemon-herb mixture.
Carefully remove the sheet pan from the oven, move 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 chicken breast.
Return the pan to the oven and roast for an additional 18-22 minutes, or until the chicken reaches an internal temperature of 165°F and the asparagus is bright green.
Let the chicken rest for 5 minutes before slicing to keep it juicy, then serve immediately with the roasted vegetables.