Preheat oven to 350 degrees. In a large bowl, toss together cereals, pretzel rounds, olive oil and Parmesan cheese.
Spread mixture in a single layer on a rimmed baking sheet. Bake until cheese is melted and cereal is crisp and lightly golden, 15 to 20 minutes. Serve at room temperature.
This mix will keep for up to one week when stored in an airtight container at room temperature.