Begin by bringing a large pot of salted water to a rolling boil over high heat. Add the tri-color rotini pasta and cook according to package instructions until al dente, typically around 7-9 minutes. Once cooked, drain the pasta in a colander and rinse it under cold water until completely cooled.

In a large mixing bowl, combine the cooled pasta with halved cherry tomatoes, sliced pepperoni, diced red onion, and chopped green bell pepper. Next, add the cubed mozzarella and grated parmesan cheese, along with any olives you prefer. Toss everything together gently to distribute the ingredients evenly.

In a separate small bowl, whisk together the olive oil and red wine vinegar until emulsified. Then stir in the Italian seasoning, garlic powder, salt, pepper, and red pepper flakes if desired. Mix until well incorporated.

Pour the homemade vinaigrette over the pasta salad mixture in the large bowl. Use a spatula or large spoon to gently toss all the ingredients together.

Cover the bowl with plastic wrap or transfer the salad to an airtight container, then refrigerate for at least 1 hour.