Bring a large pot of salted water to a boil. Cook rotini until al dente, about 8 to 10 minutes. Drain, rinse with cold water, and drizzle with a little oil.

In a small bowl, whisk olive oil, vinegar, garlic, mustard, oregano, salt, and pepper until emulsified.

In a large bowl, combine pasta, tomatoes, mozzarella, salami, olives, bell pepper, onion, and parsley. Pour dressing over and toss to coat. Cover and refrigerate at least 2 hours.

Remove from fridge, stir, and taste. Adjust with extra vinegar or salt. Garnish with more parsley and Parmesan if desired. Serve.