Bring a large pot of salted water to a rolling boil. Add rotini and cook until al dente according to package directions. Drain, rinse under cold water to stop cooking, and drain again thoroughly.

Preheat oven to 400°F (200°C). Lay bacon slices on a foil-lined baking sheet and bake for 12–15 minutes, until extra crispy and the internal temperature reaches at least 145°F (63°C). Transfer to paper towels to drain, then crumble into bite-sized bits.

In a large mixing bowl, whisk together the ranch dressing and sour cream until smooth and combined. Season with black pepper and a tiny pinch of salt if needed.

Add the cooled pasta, crispy bacon crumbles (reserve a spoonful for garnish), cheddar cheese, cherry tomatoes, green onions, and chives to the bowl with the dressing. Gently fold everything together until evenly coated.

Cover and refrigerate for at least 30 minutes (up to overnight) to let flavors meld. Before serving, give it a gentle stir, top with reserved bacon and extra chives, and serve chilled.