Bring a large pot of salted water to a rolling boil over high heat. Add the tri-color rotini pasta and cook for about 8 minutes, or until al dente. Drain and rinse under cold water.

In a large mixing bowl, combine mayonnaise, sour cream, dry ranch dressing mix, garlic powder, and milk. Whisk until fully blended and creamy.

Add the cooled tri-color rotini pasta to the dressing. Incorporate the chopped bacon, diced tomato, sliced black olives, and shredded cheddar cheese. Gently toss until coated.

Cover and refrigerate the salad for at least 2 hours to allow flavors to meld.

Before serving, stir the chilled pasta salad gently. If dry, add a splash of milk to reach desired creaminess.