Bring a large pot of generously salted water to a rolling boil. Add the rotini and cook until al dente, about 8-10 minutes.
Drain the pasta and immediately rinse under cold running water for 1-2 minutes to stop the cooking. Drain completely and let dry.
Halve the cherry tomatoes, dice both bell peppers, and finely dice the red onion. If desired, soak the onion in cold water for 10 minutes to mellow the bite.
Slice the black olives, halve the kalamata olives, quarter the pepperoni slices, cube the provolone, and tear the basil by hand.
In a small bowl or jar, whisk together the Italian dressing, red wine vinegar, oregano, dried basil, garlic powder, and optional red pepper flakes until combined.
Add the cooled pasta to a large mixing bowl and toss with half the dressing while still slightly warm so it absorbs deeply.
Add the pepperoni, bell peppers, red onion, cherry tomatoes, black olives, kalamata olives, mozzarella pearls, provolone, and torn basil.
Pour the remaining dressing over the salad and toss gently until everything is evenly coated. Sprinkle with Parmesan and toss once more. Season with salt and pepper to taste.
Cover tightly and refrigerate for at least 1 hour, preferably overnight, to let the flavors meld. Toss again before serving, adding extra dressing if needed.