Cook the pasta: Bring a large pot of salted water to a boil, add the tri-color rotini pasta, and cook according to package instructions until al dente (8-10 minutes). Drain and rinse under cold water.

Combine salad ingredients: In a mixing bowl, add the cooled rotini pasta, halved cherry tomatoes, sliced pepperoni, diced red onion, and chopped green bell pepper. Fold in the mozzarella, grated parmesan cheese, and sliced olives.

Prepare the vinaigrette: In a separate bowl, whisk together olive oil and red wine vinegar. Then incorporate Italian seasoning, garlic powder, salt, pepper, and red pepper flakes.

Dress the salad: Pour the vinaigrette over the salad mixture and gently toss until everything is well coated.

Chill and serve: Cover the bowl and refrigerate for at least 1 hour to allow flavors to meld. Serve chilled or at room temperature after letting it sit.