Lightly spray the insert of a 6- or 7-quart slow cooker with cooking spray.
In a small bowl, mix together the salt, black pepper, garlic powder, and Italian seasoning. Trim excess fat from the roast and season each side with about one-third of the seasoning mixture.
2 teaspoons fine sea salt, 1 teaspoon fresh ground black pepper, 1 teaspoon garlic powder, 2 teaspoons Italian seasoning, 4 pound boneless beef chuck pot roast
Place the seasoned roast in the slow cooker. Pour the tomato sauce over the top, then add the sliced green bell peppers, onions and pepperoncini (make sure to drain it). Sprinkle the remaining third of the seasoning over the vegetables and drizzle with the reserved pepperoncini liquid.
15 ounces tomato sauce, 2 green bell peppers, 2 yellow onions, 12 ounces jar sliced pepperoncini
Cover and cook on low for 10-12 hours, or on high for 5-6 hours, until the beef is tender and shreds easily.
Once the beef is done, preheat your oven to 250°F. Open up the rolls slightly and toast for just a few minutes.
10 crusty sandwich rolls
Using two forks, shred the beef in the slow cooker—it should be very tender and fall apart easily. Mix well with the peppers and onions.
Using tongs or a slotted spoon, scoop the beef mixture onto the bottom half of each sandwich roll, letting excess liquid drain away to prevent soggy sandwiches.
10 crusty sandwich rolls
Top each sandwich with additional pepperoncini if desired and slices of Provolone cheese. Place the sandwiches in the oven for a few minutes, just until the cheese melts.
20 slices Provolone cheese
Serve the sandwiches immediately, with extra pepperoncini on the side if you like. Enjoy!