In a jar with a tight-fitting lid, combine the olive oil, red wine vinegar, lemon juice, and Dijon mustard. Add the oregano, basil, garlic powder, onion powder, salt, red pepper flakes, and black pepper. Seal the jar tightly and shake vigorously for 30 seconds until the dressing is well emulsified and the spices are evenly distributed. Set aside at room temperature while you prepare the other components.

Bring a large pot of salted water to a rolling boil. Add the rotini and cook according to package directions until al dente, usually takes 8-10 minutes. Drain the pasta in a colander but do not rinse it.

While the pasta cooks or immediately after draining it, dice the pepperoni into bite-sized pieces, chop the sun-dried tomatoes into ¼-inch bits, crumble or dice the feta cheese, and finely chop the fresh parsley. Arrange all prepped ingredients in separate small bowls.

Transfer the drained pasta to a large mixing bowl. Pour the dressing from Step 1 over the warm pasta and stir well to coat every piece. Add all the prepared ingredients from Step 3 and fold everything together gently but thoroughly.

Transfer the pasta salad to an airtight container or cover the bowl tightly with plastic wrap. Refrigerate for at least 8 hours, preferably 12 hours, which allows the flavors to meld together.

Remove the pasta salad from the refrigerator and give it a good stir to redistribute any dressing that may have settled at the bottom. Taste and adjust seasonings if needed. Serve cold or at room temperature.