Score steaks on both sides.
Use tenderizer according to label directions.
Spread one side of steaks with horseradish.
Combine onion, celery, butter, and seasoned salt; spread on steaks.
Roll up jelly roll style, fasten with skewers, and tie with string.
Balance meat rolls on spit; secure with holding forks.
Place medium coals on both sides of drip pan.
Attach spit so meat is over drip pan; turn on motor.
Roast over medium coals till done, about 45 minutes.
Let stand a few minutes; remove strings and skewers.
Heat sour cream over low heat; do not boil.
Carefully cut meat rolls into thin slices and place on bread.
Spoon warm sour cream over meat.
Sprinkle with paprika, if desired.