Slice the roll so that you are left with top and bottom pieces of equal thickness.
Remove and discard the thick rib section from the romaine then place one on top of the other. Starting at one of the narrow ends, roll them tightly and then slice them into ¼ inch strips.
Starting at the narrow end, cut the tomato into ¼ inch slices.
Assembly
Distribute the vinegar and most of the oil on the cut sides of the roll. Reserve some oil for step 4 below.
Sprinkle salt and pepper on the cut sides of the roll.
Place the tomato slices and then the cheese slices on the bottom half of the roll.
Place the sliced lettuce on top of the cheese and season with oregano and additional salt, pepper and oil.
Place the top section of the roll on the sandwich, cut it and serve.
Notes
Sandwich is ready to be eaten immediately but some people feel that wrapping it in plastic wrap and allowing it sit for several hours improves the flavor.