If the roll is whole, slice lengthwise leaving a hinge if desired. Lightly toast the inside faces of the roll under a broiler or in a toaster oven for 1–2 minutes until just golden (optional). Spread mayonnaise on one cut side (about 2 tbs) and spread marinara on the other cut side (about 3 tbs) or use only the sauce(s) you prefer.

Cooked Vegetables

Sauté mushrooms, onions and peppers

Heat 1 tbs olive oil in a skillet over medium-high heat. Add the sliced mushrooms and cook undisturbed 2 minutes, then add the sliced onions and green pepper. Season with 1/4 tsp salt and 1/8 tsp black pepper. Sauté, stirring occasionally, until vegetables are softened and edges are slightly caramelized, about 6–8 minutes. Taste and adjust seasoning. Remove from heat and drain any excess liquid.

Assemble & Finish

Layer cheese and warm vegetables

Place the cheese slices on the bottom (marinara) half of the roll. Spoon the warm sautéed mushroom, onion and pepper mixture evenly over the cheese so heat slightly melts the cheese. If you prefer melted cheese, place the assembled open sandwich briefly under a broiler (30–60 seconds) until cheese softens — watch closely.

Add fresh toppings

Over the warm vegetables, arrange tomato slices, shredded lettuce and sliced black olives evenly. Sprinkle optional red pepper flakes if desired.

Close and serve

Fold the top half of the roll (mayo side) over the fillings, press gently to compact, and cut in half if desired. Serve immediately so warm vegetables and melted cheese contrast with crisp lettuce. Provide extra marinara or mayo on the side if desired.