Preheat your oven to 400°F (200°C) and line two baking sheets with parchment paper.

Toss cauliflower and sweet potatoes with olive oil, cumin, salt, and pepper on one sheet. Toss red bell peppers and onion with same seasonings on another sheet. Roast for 30-35 minutes.

Lower the oven temperature to 350°F (175°C) and grease a 9-inch square baking dish with olive oil.

In a medium bowl, mix fresh cilantro into the red salsa.

Spread ½ cup of the salsa mixture in the bottom of the prepared baking dish. Layer corn tortillas, half of the black beans, one-third of the roasted veggies, half of the spinach, and a third of the cheese. Repeat the layers.

Top with another layer of tortillas, remaining salsa, and cheese. Cover with foil and bake for 20 minutes, then remove foil and bake for an additional 10 minutes.

Let casserole cool for 10 minutes before serving, garnishing with additional cilantro.