In a large pot, bring salted water to a rolling boil. Add the tri-color rotini pasta and cook according to package instructions until al dente, typically about 8-10 minutes. Once cooked, drain the pasta in a colander and rinse under cold water.

Place the cooled rotini pasta in a large mixing bowl. Add in halved cherry tomatoes, sliced pepperoni, red onion, bell pepper, mozzarella cheese, grated parmesan, and olives. Stir gently to distribute the ingredients.

In a separate bowl, whisk together olive oil, red wine vinegar, Italian seasoning, garlic powder, salt, pepper, and red pepper flakes until well combined.

Pour the vinaigrette over the pasta and vegetable mixture. Toss everything together gently to coat evenly.

Cover the bowl with plastic wrap or a lid and refrigerate for at least 1 hour to allow flavors to develop.

When ready to serve, let the salad sit at room temperature for about 20-30 minutes. Toss again before serving.