Cook rotini in a pot of boiling water for 7-9 minutes, or until done. Drain and rinse pasta under cold water until cool.
Meanwhile, in a small bowl, whisk together oil, parmesan cheese, vinegar, oregano, garlic powder, salt and pepper.
Place cooked pasta, vinegar mixture, and remaining ingredients in a large mixing bowl, turning to coat all ingredients. Refrigerate at least 2 hours before serving.