Preheat oven to 375 degrees.
Wash sweet potatoes and chop into cubes.
Chop purple onion.
Combine sweet potatoes, onions, olive oil, honey, cinnamon, and rosemary in a bowl and stir until coated.
Spray cookie sheet with cooking spray, then spread sweet potato cubes evenly.
Cook for 35-45 minutes, stirring periodically during cooking.