Slice baguette into 1/2-inch rounds and toast until light brown on both sides. Combine mayonnaise, horseradish, and TABASCO® Sauce in a small bowl and mix well. Spoon a generous teaspoon of sauce onto each toast round; mound slices of roast beef on sauce and top with freshly ground pepper. Serve on a large round plate or tray.
Makes about 30 crostini.