Season all sides of roast with 1 packet of dressing mix and put into crock pot. Mix remaining 2 packets of dressing with 1c. of water.
Pour water mixture over roast.
Cover crockpot and cook on high for 4-5 hours.
Remove roast from crockpot and shred. ( If roast is not shredding easily, it needs to cook longer ) Put shredded beef back into crockpot. Add the entire jar of pepperoncini to the beef. Cook the beef with the peppers for 30 more minutes.
Top rolls with shredded beef and peppers and top each sandwich with mozzarella cheese.