Preheat your oven to 425°F and line a baking sheet with parchment paper.
Wash and dry the sweet potatoes. Slice them evenly into 1/2-inch rounds to ensure even cooking.
Place the sweet potato slices in a large bowl. Drizzle with olive oil, then sprinkle with salt, pepper, and, if desired, garlic powder and cinnamon. Toss until each slice is coated.
Arrange the slices in a single layer on the prepared baking sheet. Bake for about 25-30 minutes, flipping the slices halfway through, until they are tender and lightly browned. Garnish with chopped rosemary.