Bring a large pot of lightly salted water to a rolling boil; cook the rotini in the boiling water until the pasta is cooked through yet firm to the bite, about 8 minutes. Drain. Rinse under cold running water until completely cooled; drain thoroughly.
Whisk the salsa, mayonnaise, sour cream, black beans, Mexican-style corn, red bell pepper, green onions, black olives, garlic powder, cumin, cilantro, salt, and pepper together in a large bowl; add the cooled pasta and stir to coat evenly. Cover the bowl with plastic wrap and refrigerate 2 hours to overnight before serving.
