Cook the rotini pasta according to package instructions until al dente. Drain and rinse under cold water to cool.
In a large mixing bowl, combine the cooled pasta, cherry tomatoes, and mozzarella balls.
Add the basil pesto, grated Parmesan cheese, and olive oil to the pasta mixture. Toss gently to combine until everything is evenly coated.
Season with salt and pepper to taste. Adjust the seasoning if necessary.
Cover the salad and refrigerate for at least 30 minutes to allow the flavors to meld.
Before serving, give the salad a gentle toss and garnish with fresh basil leaves if desired.