Bring a large pot of water to a rolling boil. Add the rotini pasta and cook until al dente, 9β11 minutes, then drain and rinse under cold water until fully cool; shake off excess water and set aside.
Make the dressing: In a measuring cup or jar, whisk together the extra-virgin olive oil, red wine vinegar, Dijon mustard, finely grated garlic, dried oregano, dried basil, sugar, fine sea salt, and finely ground black pepper until emulsified.
Prepare the mix-ins: Halve the cherry tomatoes; dice the cucumber (seed if watery); dice the red bell pepper; thinly slice the red onion; slice the pitted black olives; halve the fresh mozzarella balls; chop the parsley.
In a large bowl, combine the cooled rotini, cherry tomatoes, cucumber, red bell pepper, red onion, black olives, mozzarella, and parsley. Pour the dressing over and toss until everything is evenly coated.
Cover and refrigerate 20β30 minutes to let the flavors meld, stirring once; itβs ready when the pasta has absorbed some dressing and the salad tastes bright and balanced. Toss again before serving and adjust seasoning if needed.