Line a heavy, rimmed baking sheet with foil and scatter the butternut squash, onion, and jalapeño peppers on it.
Drizzle the oil on the vegetables, and sprinkle with the salt, cumin and chili powder. Toss well to coat the veg.
Roast at 400' for 40 minutes, stirring half way through, until the squash is soft, and the onions and peppers are caramelized around the edges.
While the veggies are roasting, brown the chorizo in a large skillet, breaking it up into fine crumbles, until no longer pink in the center.
Remove the veggies from the oven and reduce oven temp to 375'
Add the can of drained and rinsed black beans to the squash and onion mix and mix well.
Assemble the casserole: Ladle 1/2 cup of enchilada sauce in the bottom of a casserole dish and cut two tortillas to fit the bottom of the dish. Spoon in 1/3 of the squash and bean mixture evenly over the tortillas, topped with 1/3 of the chorizo, 1/3 of the spinach, and 1/2 cup of cheese , spread evenly. Ladle 1/2 cup of enchilada sauce over the cheese.
Repeat layers two more times. Top with final layer of tortillas, sauce and remaining cheese.
Cover casserole with foil and bake at 375' for 30 minutes. Casserole can be assembled in advance and refrigerated or frozen. If baked from refrigerator, bake for 45 min. before removing foil. If baking from frozen, bake for one hour and 30 min.
Remove foil and bake for another 10-15 minutes until the cheese is bubbly and the tortillas are starting to brown.