Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Slice the sweet potatoes into ¼-inch thick rounds.
Use a pumpkin-shaped cookie cutter or a small paring knife to cut each slice into a pumpkin shape. Then carve out little jack-o’-lantern faces (eyes, nose, mouth) – be gentle so the pieces don’t break.
Place the pumpkin slices on the prepared baking sheet. Drizzle with olive oil and sprinkle evenly with salt, pepper, garlic powder, onion powder, and fresh rosemary leaves.
Roast for 45 minutes, until the sweet potatoes are tender all the way through. Let them rest for 5 minutes before serving.