Preheat your oven to 350°F (175°C).
In a large bowl, combine the cooked rice, black beans, corn, half of the cheese, diced chicken or beef (if using), cumin, garlic powder, onion powder, salt, and pepper. Mix well until all ingredients are evenly combined.
Warm the tortillas in the microwave for about 30 seconds to make them pliable.
Spoon about 1/2 cup of the filling mixture onto the center of each tortilla. Roll the tortilla tightly, folding in the sides as you go, to create a burrito.
Place the rolled burritos seam-side down in a greased 9x13 inch baking dish.
Pour the green chili enchilada sauce over the top of the burritos, ensuring they are well covered. Sprinkle the remaining cheese on top.
Cover the dish with aluminum foil and bake for 20 minutes. Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden.
Remove from the oven and let cool for a few minutes. Garnish with fresh cilantro if desired and serve with sour cream on the side.