1. Heat walnuts in a small nonstick skillet over medium-low heat, stirring occasionally, 5 to 6 minutes or until lightly toasted.
2. Remove rolls from packages. (Do not separate rolls.) Cut rolls in half horizontally, creating 1 top and 1 bottom per package. Spread preserves on cut sides of top of rolls; sprinkle with walnuts. Spread mustard-mayonnaise blend on cut sides of bottom of rolls; top with beef and cheese. Sprinkle with salt and pepper to taste, if desired. Cover with top halves of rolls, preserves sides down, and wrap in aluminum foil.
3. Bake at 325° for 20 to 25 minutes or until cheese is melted. Slice into individual sandwiches.
Note: To make ahead, prepare recipe as directed through Step 2, and freeze up to 1 month. Thaw overnight in refrigerator, and bake as directed in Step 3. For testing purposes only, we used Rainbo Dinner Time Rolls, Hellmann's Dijonnaise Mustard, and Boar's Head Londonport Top Round Seasoned Roast Beef.