Split and toast 8 onion rolls.
Mix one 15 ounce can corned beef hash, 1/3 cup dairy sour cream, 1 tablespoon sweet pickle relish, and 1 teaspoon prepared horseradish.
Spread about 1/4 cup on bottom half of each roll.
Broil 3 to 4 inches from heat till heated through, about 5 minutes.
Top each sandwich with a slice of tomato and a slice of process American cheese; broil just till cheese melts.
Cover with tops of rolls.