Lightly grease the inside of your slow cooker with nonstick cooking spray.
Separate the deli-sliced roast beef and layer the slices evenly across the bottom of the slow cooker.
Spread the beef gravy over the roast beef, making sure the slices are well covered.
Use tongs to gently toss the slices so each piece is coated in gravy.
Cover the slow cooker and cook on LOW for approximately 2 hours, or until the beef is thoroughly heated.
About 10 minutes before serving, slice the hoagie rolls in half and place them on a baking sheet. Toast in a preheated 400°F (200°C) oven for 3–5 minutes, until lightly golden and crisp.
Use tongs to divide the warm beef among the toasted rolls, spooning a little extra gravy over the meat if desired.
Place one slice of provolone cheese on each sandwich. Let the residual heat melt the cheese, or briefly return the assembled sandwiches to the oven until melted.
Serve immediately with your favorite side dishes and enjoy your easy homemade hot beef sandwiches.
