Lightly grease a large rectangular baking dish (at least 8x12 inches). Set aside.
Add the chopped sweet potato into a medium pot of water and bring to a boil. Reduce heat and simmer for 9 to 15 minutes, uncovered, until fork tender. Drain and set aside. You can also steam the potatoes until tender, instead of boiling.
In a large skillet, stir together the oil, onion, and garlic and sauté over medium heat for around 3 to 5 minutes until the onion softens. Season with a pinch of salt and pepper.
Preheat the oven to 350°F.
Add the chopped roasted peppers, sun-dried tomatoes, cooked/drained sweet potato, spinach, and black beans. Cook for 3 to 5 minutes over medium-high heat, until the spinach is wilted.
Stir in 1/4 cup plus 2 tablespoons of homemade enchilada sauce, followed by the lime juice, chili powder, cumin, and salt. Adjust seasonings to taste, if desired.
Add 3/4 cup of Enchilada Sauce onto the bottom of your casserole dish and spread it out evenly.
Scoop 3/4 cup of the sweet potato and black bean filling onto each tortilla. Roll up the tortilla and place it, seam side down, in the casserole dish. Repeat for the rest. If you have any leftover filling, you can spread it on top of the tortillas. Spread all of the remaining enchilada sauce on top of the tortillas until they are completely covered in sauce.
Bake the enchiladas, uncovered, at 350⁰F for 20 to 25 minutes, until the sauce is a deep red color and the enchiladas are heated through.