Preheat the oven to 400 degrees Fahrenheit.
Place the rolls on a baking sheet or baking dish lined with parchment paper. Without separating the rolls, cut the tops off using a serrated knife and set the tops aside.
Layer 6 slices of cheese, ham, pepperoni, and salami on top of the bottom layer of rolls, and bake in the preheated oven for 6 minutes until the cheese melts.
Add the lettuce, onion, mayonnaise, and half of the Italian seasoning to a medium mixing bowl and stir to combine.
Remove the bottom layer from the oven and layer the lettuce mixture, tomatoes, and the remaining cheese.
Place the top layer of the rolls on top. Brush the melted butter on top of the rolls and sprinkle the remaining Italian seasoning on top.
Bake the sliders in the preheated oven for 15 minutes, or until the top is golden brown.
Slice each slider apart and serve warm.