Preheat oven to 350°. In a large bowl, mix together egg, meat loaf seasoning, tomato sauce and bread crumbs. Add ground beef; mix well. On a piece of waxed paper, pat meat mixture into an 18x9-in. rectangle. Top with layers of ham, cheese and mushrooms. Roll rectangle, jelly-roll style, starting from narrow end. Pinch edges to seal. Place seam side down in a shallow baking pan. Bake until no pink remains, about 1-1/4 hours. Let stand several minutes before slicing. Freeze option: Securely wrap and freeze cooled meat loaf in foil. To use, partially thaw in refrigerator overnight. Unwrap meat loaf; reheat on a greased 15x10x1-in. baking pan in a preheated 350° oven until heated through and a thermometer inserted in center reads 165°.
To make soft bread crumbs, tear bread into pieces and place in a food processor or blender. Cover and pulse until crumbs form. One slice of bread yields 1/2 to 3/4 cup crumbs.