Preheat the oven to 350 degrees F. Place the tomato sauce in a 9 by 13-inch baking dish and place in the oven to heat. In oven-proof dutch oven, saute mushrooms over high heat until they stop giving off juice and are somewhat dry. Add garlic part way through this. Add sundried tomatoes near end. Cool slightly. Add beaten eggs and mix well. Add bread crumbs, cheese, herbs and mix until it forms a thick paste. Brush the pounded flank steak with the olive oil. Lay proscuitto over steak. Spread the filling evenly over the meat. Roll tightly starting with a long side so the meat grain runs the length of the roll. Tie with butchers twine. When sliced, it will be sliced across the grain. Wipe out pan. Heat 1 to 2 tablespoons of vegetable oil and sear all sides of the rolled meat. Add tomato sauce. Roll meat around till it is coated in sauce. Cover with a tin foil tent so that the foil is not touching the meat. Braise for 35 minutes or, up to 3 hours.