Bring a large pot of lightly salted water to a boil. Add the pasta, and cook for 8 to 10 minutes, or until tender. Drain, and run under cold water to cool. Drain again, and transfer to a large bowl.
In a separate bowl, stir together the mayonnaise, sour cream and celery root. Stir this into the noodles to coat. Fold in the grapes, turkey and celery. Chill until serving.
To serve, place a bed of romaine lettuce onto serving plates. Top with the turkey pasta salad.
