Bring a large pot of salted water to a boil. Cook the rotini pasta according to package instructions until al dente. Drain and rinse under cold water to stop the cooking process. Set aside to cool.

Cook the bacon in a skillet over medium heat or bake it in the oven until crispy. Transfer to paper towels to drain excess grease, then crumble into small pieces.

Chop the romaine lettuce into bite-sized pieces. Slice the cherry tomatoes in half and chop green onions if using.

In a small bowl, whisk together mayonnaise, sour cream, ranch seasoning, garlic powder, lemon juice, and black pepper until smooth.

In a large bowl, combine the cooled pasta, bacon, tomatoes, and dressing. Toss until evenly coated.

Gently fold in the chopped lettuce and green onions just before serving. Chill for about 30 minutes for the best flavor.