Cook the rotini pasta according to package directions until al dente. Drain and rinse with cold water until completely cooled.
Transfer the cooled pasta into a large mixing bowl. Add the cooked chicken, cherry tomatoes, celery, green onions, and crumbled blue cheese. Toss gently to combine all the ingredients evenly.
In a separate bowl, whisk together the mayonnaise, ranch dressing, buffalo sauce, garlic powder, onion powder, salt, and black pepper until smooth and creamy. Taste and adjust the buffalo sauce if you want more heat.
Pour the buffalo dressing over the pasta mixture and toss thoroughly until all the pasta and ingredients are fully coated in the creamy dressing.
Cover the bowl and refrigerate the pasta salad for at least 30 minutes before serving so the flavors blend together perfectly.
Before serving, stir the pasta salad gently and garnish with extra green onions or blue cheese crumbles if desired. Serve chilled.