Lightly mix the ingredients together in a large bowl. Form the meatloaf on a grilling plank and let it rest a few minutes.
Place the grilling plank over medium direct heat (350°F/177°C). Cook for approximately 2 hours. With one hour left, take additional marinara sauce and brush it on top of the meatloaf. Repeat every 15-20 minutes until a nice tomato glaze has formed on top. The meatloaf is cooked when the meat registers 165°F/74°C in the center.
Let the meatloaf rest and cool a bit. Take the Cobblestone Bread Co (TM) Toasted Onion Rolls and lightly grill them for about 30 seconds to get warm. Slice the meatloaf thick and assemble the sandwich by placing the meatloaf on the roll and topping it with a slice of mozzarella cheese.
Makes 4 sandwiches