Bring a large pot of salted water to a boil and cook the rotini pasta according to package instructions until al dente.
Drain the pasta and rinse it under cold water until completely cooled to stop the cooking process and prevent sticking.
While the pasta cooks, fry the bacon in a skillet over medium heat until crispy, then transfer it to a paper towel-lined plate and crumble once cooled.
Transfer the cooled pasta to a large mixing bowl.
Add the crumbled bacon, cheddar cheese cubes, cherry tomatoes, red onion, and green onions to the bowl with the pasta.
In a separate bowl, whisk together mayonnaise, sour cream, ranch seasoning mix, milk, garlic powder, dried parsley, salt, and black pepper until smooth and creamy.
Pour the ranch dressing over the pasta mixture and toss gently until everything is evenly coated.
Sprinkle fresh parsley over the salad and mix lightly once more.
Cover and refrigerate the pasta salad for at least 30 minutes before serving so the flavors can blend together.
Toss again before serving and garnish with extra bacon or green onions if desired.