In a saucepan, combine the beef broth and Cajun seasoning. Heat over medium heat until warmed through.
Add the sliced roast beef to the broth mixture and simmer for about 5 minutes, allowing the beef to absorb the flavors.
While the beef is simmering, slice the hoagie rolls lengthwise, being careful not to cut all the way through.
Spread mayonnaise on the inside of each roll. If desired, add hot sauce for extra flavor.
Layer the shredded lettuce and tomato slices inside each roll.
Using tongs, remove the beef from the broth and place it generously into each prepared hoagie roll.
Drizzle a little of the broth over the beef in each sandwich for added moisture.
Season with salt and pepper to taste, then close the rolls and serve immediately.