Preheat oven to 400 degrees. Slice sweet potatoes 1/2 inch thick, and place in a single layer on a lightly oiled baking sheet. Roast until browned on bottoms, 30 to 35 minutes. We topped these with spicy black beans, crumbled cotija cheese, and cilantro leaves. You can also try them with the cheese of your choice and chutney, salsa, or pesto.