Preheat oven to 400ºF. Line a baking tray with parchment paper. Lightly oil a 9-inch square baking dish and set aside. To make the sweet potato filling, place sweet potatoes, bell pepper, and onion on the baking tray in a pile. Drizzle with the oil. Sprinkle with chili powder, cumin, cinnamon, salt, and cayenne. Use your hands to toss together, coating everything with spices and oil. Arrange in a single layer. Place the tray in the oven and roast for about 20 minutes, or until sweet potatoes are just fork-tender, but not mushy and the bell peppers and onions are tender. When done, remove from the oven and reduce temperature to 375ºF.

To make the black beans, place them in a bowl with about ¾ cup of salsa and salt. Use a wooden spoon or fork to partially mash the beans.

To make the Cashew-Herb Cream, add cashews, cilantro, garlic, water, lime juice, and salt to a blender. Blend on high speed for about 1 to 2 minutes, until smooth and creamy. Add more water, by the tablespoon, if necessary to help with blending. Taste and adjust flavors by adding more salt or lime juice if you like.

To assemble, lay a tortilla flat on a cutting board. Spread about 1/4 cup of black bean-salsa mixture on the tortilla, leaving a 1/4-inch border. Arrange about ⅓ to ½ cup of sweet potato mixture evenly over the black beans about 1/3 of the way up from the bottom edge closest to you. Lay 2 to 3 slices of avocado across the sweet potatoes. Using a firm hand, begin rolling away from you, while folding and tucking the ends in. Place burritos seam side down in the prepared baking dish and repeat until ingredients have been used. Drizzle about ½ of the Cashew-Herb Cream over burritos. Place the baking dish in the oven and bake for 10 to 15 minutes, until heated through. Serve immediately, garnished with remaining cashew cream, salsa, and cilantro. Alternatively, you can serve without baking, or chill and serve as a cold sandwich.