Place the thinly sliced ribeye in a bowl or Ziploc bag. Season it with with seasoned salt, garlic powder, onion powder, rosemary, and Worcestershire sauce. Toss until the meat is evenly coated. Let it sit for about 10 minutes while you prepare the vegetables.
Heat olive oil in a large skillet over medium-high heat. Add the thinly sliced onions and bell peppers and sauté for about 5–6 minutes, until softened and slightly caramelized. Slide the vegetables to one side of the skillet.
Add the seasoned ribeye to the empty side of the skillet. Cook the steak for about 3–4 minutes, stirring frequently, until it is just cooked through.
Mix the peppers and onions together with the steak, then place mozzarella slices over the steak mixture, cover the skillet for about 1 minute, and allow the cheese to melt.
While the cheese is melting, make a sauce (optional). In a small bowl, mix together mayonnaise, mustard, and ketchup until smooth.
Spread the sauce inside your toasted hoagie rolls, then pile the cheesy steak mixture inside. Serve immediately while warm.