Cook the rotini pasta according to package instructions until al dente. Drain and rinse under cold water to cool.
In a large bowl, combine the cooled pasta, cherry tomatoes, cucumber, bell pepper, black olives, mozzarella cheese, and red onion.
Drizzle the Italian dressing over the pasta mixture and toss gently to combine. Season with salt and pepper to taste.
Transfer the salad to a large serving dish or layer it in a trifle bowl for a beautiful presentation.
Chill in the refrigerator for at least 30 minutes before serving to allow the flavors to meld.
Garnish with fresh basil leaves before serving, if desired.