Preheat oven to 300°F. In a large saucepan over medium heat combine the soup, Worcestershire sauce, and water. Stir gently. Add roast beef slices. Heat thoroughly and until soup being to bubble.

Once the roast beef is warm, evenly divide it among the 4 hoagie rolls. Top with 2 slices of Provolone or about 1/2 cup of shredded Mozzarella.

Place each sandwich on a rimmed baking sheet. Heat sandwiches in the oven until cheese is melted, about 6 - 9 minutes. Ladle onion soup into small ramekins and serve for dipping.