Preheat an electric griddle or stovetop griddle over medium-high heat. On one half of the griddle, place the mushrooms, onion and pepper. On the other side, place the roast beef. Cook and stir each group separately, chopping the beef into smaller pieces as it cooks, and seasoning with salt and seasoned salt.
When the vegetables are tender and the beef is hot, place the slices of provolone cheese over the beef to melt. Turn off the griddle. Scoop the cheesy grilled beef into sandwich rolls, and top with the onions and peppers.