Combine ground chuck, onion, eggs, crackers, milk, salt, pepper and garlic salt in large bowl.Mix well.Add more milk, if dry.Turn ground chuck mixture onto long piece of waxed paper.Pat mixture into rectangle, about 6 x 13 x 1/4" thick.Spread mozzarella cheese over mixture to about 1" from edges.Start from one end and lift waxed paper and roll mixture into a log shape.Carefully, place in large oven-proof casserole dish, seam down.Pinch ends to seal.Pour tomato sauce over mixture.Bake 375 degrees for 1 to 1/2 hours or until middle is done.