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. Stir in 1 tsp olive oil to prevent sticking, if desired.

Drain the pasta thoroughly and rinse with cold water until completely cool. This stops the cooking process and prevents the pasta from clumping. Set aside in a large mixing bowl.

While the pasta cooks, prepare all the vegetables and add-ins. Halve the cherry tomatoes, dice the English cucumber, thinly slice or finely dice the red onion, slice the pitted black olives, and dice the red bell pepper. Halve the fresh mozzarella balls if they are large ciliegine.

Add all the prepared vegetables, pepperoni slices, fresh mozzarella, and chopped fresh parsley to the bowl with the cooled pasta.

In a separate small bowl, whisk together the red wine vinegar, extra virgin olive oil, Dijon mustard, minced garlic, dried oregano, dried basil, red pepper flakes (if using), salt, and black pepper until well combined and emulsified.

Pour the prepared vinaigrette over the pasta and salad mix-ins in the large bowl. Toss everything gently until the pasta and all ingredients are evenly coated with the dressing.

Cover the bowl and refrigerate for at least 1-2 hours before serving. This allows the flavors to meld and develop. For best results, chill for at least 4 hours or overnight.

Give the salad another good toss just before serving. Taste and adjust seasonings if necessary.