Cook the rotini pasta according to package directions, adding about 1 teaspoon of salt to the boiling water.
Drain the pasta and rinse it under cold water. Transfer to a mixing bowl and pour in 1/3 cup of pickle juice. Stir gently and let sit.
Dice the dill pickles, cube the Colby Jack cheese, and finely chop the white onion.
Drain excess pickle juice from the pasta, then return it to the bowl with the chopped pickles, cheese, and onion. Stir until combined.
In a separate bowl, mix mayonnaise, sour cream, additional dill pickle juice, fresh dill, salt, and pepper. Pour over the pasta mixture.
Gently stir until everything is well coated. Chill for at least 1–2 hours before serving.