Step 1: Preheat the oven to 400º F.
Step 2: Prepare two baking sheets with parchment paper.
Step 3: Cut the sweet potatoes into ¼  inch thick slices.
Step 4: With a cookie cutter or a knife, cut the slices into pumpkin shapes.
Step 5: Using a small knife or a cutting tool with a sharp and thin blade, cut the faces on your pumpkin slices. Avoid knives or cutting tools with wide blades in this process. Remove the cut pieces slowly to avoid breaking the shapes and details(teeth) in your jack-o-lantern faces.
Step 6: Place your jack-o-lanterns over the baking sheets. Drizzle with oil, sprinkle with garlic powder, onion powder, salt, pepper, and rosemary, and toss to evenly coat.
Step 7: Put them inside the oven and bake for 45 minutes, or until golden. Once done, remove them from the oven and let them sit for 5 minutes before serving. Enjoy this delicious and healthy snack or side dish with family and friends!