First make the cheese sauce by combining the Velveeta, black pepper, cayenne, and milk in a small pan. Heat over low heat, stirring occasionally, until it's melted and hot. Keep warm.Melt 2 tablespoons butter on a griddle over medium heat, then place the deli roll halves on the griddle until golden brown. Set aside. Heat 2 more tablespoons butter in a large skillet over medium-high heat. Throw in the roast beef and move it around with a spatula, breaking it up a bit as you go. Cook/warm for about a minute or so, then remove it to a plate and set it aside. Add the remaining tablespoons butter to the same skillet and throw in the onions and peppers. Reduce the heat to medium-low and cook the veggies until dark golden and soft, about 8 to 10 minutes. To build the sandwiches, place a pile of beef on the bottom half of each roll. Spoon cheese sauce over the beef. Top with peppers and onions, then top with more cheese sauce. Place the top half of the roll on top and serve immediately!Options: * Spread spicy mustard on the rolls before building the sandwiches* Mix horseradish with mayo and spread it on the rolls before building the sandwiches* Add a few dashes of Worcestershire or hot sauce to the meat and peppers while cooking.* Add prepared horseradish to the cheese sauce.