On a large cutting board, start with the chopped romaine lettuce as the base. Layer on 12 slices of pepperoni, 6 slices of salami, and 6 slices of deli ham. Add 6 slices of fresh tomato, 6 slices of provolone cheese, a handful of banana pepper rings, and thinly sliced red onions.

Using a large, sharp knife, chop all ingredients together into small, bite-sized pieces (about ½" or smaller). Drizzle the mixture with ¼ cup mayonnaise, 3 tablespoons olive oil, and 3 tablespoons red wine vinegar. Sprinkle 1 tablespoon dried Italian seasoning over the top, then season generously with salt and pepper. Toss the chopped mixture well to evenly coat with dressing and seasoning. Let sit for 5–10 minutes to allow the flavors to meld together.

Split 12 slider buns (Hawaiian rolls recommended). If desired, lightly toast them before filling. Spoon a generous portion of the chopped Italian mixture onto each bottom half, then top with the other half of the bun. Gently press each slider to help hold the filling in place. Serve immediately while fresh, or cover and chill briefly if preparing slightly ahead of time.