Bring a large pot of salted water to a rolling boil. Add the rotini pasta and cook according to package directions until al dente, usually 8-10 minutes. Drain the pasta thoroughly in a colander and rinse with cold water to stop the cooking process and prevent sticking. Set aside.

While the pasta is cooking, prepare the vegetables. Halve the cherry tomatoes, dice the cucumber, thinly slice or finely dice the red onion, slice the black olives, and dice the green bell pepper. If using regular pepperoni, quarter the slices. Halve the mini mozzarella balls.

In a small bowl or jar, combine the extra virgin olive oil, red wine vinegar, Dijon mustard, dried oregano, garlic powder, onion powder, dried basil, red pepper flakes (if using), granulated sugar, salt, and black pepper. Whisk vigorously or shake the jar until well combined and emulsified.

In a large mixing bowl, combine the cooled pasta, halved cherry tomatoes, diced cucumber, diced red onion, sliced black olives, diced green bell pepper, mini pepperoni, and halved fresh mozzarella balls.

Pour the prepared Italian dressing over the pasta and vegetable mixture. Toss gently but thoroughly to ensure all ingredients are evenly coated with the dressing.

Cover the bowl and refrigerate the Italian pasta salad for at least 30 minutes, or preferably 2-4 hours, to allow the flavors to meld and deepen. Stir again before serving.