Preheat the oven to 350˚F. Mix the mayonnaise and horseradish together and set aside.
Remove the Hawaiian Rolls from the packaging. Cut each set of 12 horizontally in half so the tops and bottoms are separated.
Lay the bottoms in a 9x13 baking dish. Spread the horseradish mixture evenly over the rolls. Next lay the roast beef and then cheese evenly over the rolls. Put the tops back on the rolls and then use a knife to cut between each roll to separate the sandwiches. (This helps for serving.)
Next, in a small bowl, whisk together the melted butter, garlic, dried onion, mustard and Worcestershire sauce. Pour over the top of the rolls and use a pastry brush to evenly spread it out and work between each roll.
Bake for 20 minutes or until the sandwiches are heated through and the cheese is melted.
