Preheat oven 375 degrees. Grease or spray a large, glass bread dish or an oblong glass or aluminum dish (9x12). Mix ingredients and place on top of wax paper on the counter. Shape into a rectangle. Drain mushrooms and sprinkle evenly over hamburger. Distribute shredded mozarella on top of the mushrooms, and press gently into the meat.
Lift wax paper with both hands on short side and roll until you reach the other end. Wet hands and tuck in the ends and seal. Lift wax paper and slide into dish so seam side is on bottom of dish.
Cook for 1/2 hour. Remove and drain any grease off. Take remainder of tomato sauce and pour evenly over top of meatloaf. Bake for 1/2 hour more.
Remove and let rest for 10 minutes. Remove meatloaf to a serving platter (I use two spatulas). Slice and serve.