Slice rolls in half. Mix together mayo, grated onion, poppy seeds, spicy mustard, horseradish, and Worcestershire. Taste it and adjust ingredients however you wish.
To assemble, spread dressing on top and bottom buns. Lay on roast beef or ham, then one or two slices of cheese (I cut them to fit the small buns.) If you're using Cheez Whiz, spread a layer on the top bun.
Wrap each sandwich in a foil square, and either keep in the fridge or bake right away. To bake the sandwiches, put them on a baking sheet in a 350 degree oven for 15 to 20 minutes. The buns should be slightly crusty and the cheese should be melted.