Brown ground turkey in a large pan over medium heat; drain if necessary. Stir in taco seasoning, Rotel, water, and macaroni. Heat to boiling. Reduce heat and cover pan. Simmer 12-14 minutes until macaroni is tender.
While pasta is cooking, make the cheese sauce: melt the butter in a saucepan. Whisk in the flour and cook, whisking for 5 minutes until fragrant and light brown in color. Whisk in the milk and bring to a boil. Whisk until smooth and thickened. Remove from heat and stir in the shredded cheddar cheese until melted. Add the salt and pepper to the cheese sauce. Pour the cheese sauce over the pasta mixture. Stir gently to combine.