Drizzle the butternut squash, corn, and onion with the olive oil. Add the chili powder, cumin, oregano, salt and pepper and toss to combine and coat with the spices.
Spread in an even layer on a baking sheet. Transfer to the oven and roast for 12-15 minutes or until the squash is tender.
Top the tostadas with the squash and corn mixture and top with the crumbled queso fresco. Add additional toppings such as salsa and cilantro and enjoy!
