Mix pepperoncini, diced tomatoes, onion, water, Italian salad dressing mix, oregano, and garlic powder in a bowl.

Place beef roast in a slow cooker.

Pour pepperoncini mixture over the roast.

Cook on low for 8-10 hours, or until meat is tender.

Remove the roast from the slow cooker and let cool slightly.

Skim fat from cooking juices.

Shred the beef with two forks.

Return the shredded beef and cooking juices to the slow cooker.

Heat through.

Serve on Italian rolls.