Begin by bringing a large pot of salted water to a rolling boil. Add the tri-color rotini pasta and cook according to package directions until al dente, usually around 7-10 minutes. Once cooked, drain the pasta and rinse it under cold water until fully cooled.

While the pasta cools, chop the cherry tomatoes, dice the green bell pepper and red onion, and slice the pepperoni. In a large mixing bowl, combine the cooled pasta with the cherry tomatoes, red onion, green bell pepper, mozzarella, parmesan, and olives.

In a smaller bowl, whisk together ½ cup of olive oil and ¼ cup of red wine vinegar until well combined. Add in Italian seasoning, garlic powder, salt, pepper, and red pepper flakes to taste.

Pour the freshly made vinaigrette over the combined pasta salad ingredients in the large bowl. Gently toss everything together using a spatula or large spoon, ensuring even coating.

After mixing, cover the salad tightly with plastic wrap or transfer it to an airtight container. Refrigerate for at least 1 hour before serving.