Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Halve the baby potatoes and trim the woody ends off the asparagus spears, then place them on the sheet pan with the cherry tomatoes and chicken breast.
In a small glass bowl, whisk together the olive oil, minced garlic, dried oregano, sea salt, and black pepper until well combined.
Drizzle the herb-oil mixture over the chicken and vegetables, using your hands or a brush to ensure everything is evenly coated.
Slice the lemon half into thin rounds and arrange them directly on top of the chicken breast to infuse it with bright citrus flavor.
Roast in the center of the oven for 22-25 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are golden and tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing to ensure the juices redistribute for maximum tenderness.
Serve the sliced chicken alongside the roasted vegetables, drizzling any remaining pan juices over the top for extra flavor.