Place roast fat side up in a slow cooker. Arrange onion slices over roast. Add beef broth, French onion soup, and beer.

Cook on low for 5 hours. Remove roast from slow cooker and allow to rest for 15 minutes. Shred meat.

In the meantime, preheat the broiler. Spread butter over the inside of the rolls. Broil until rolls are toasted, about 3-5 minutes.

Pile sliced meat along the center of each roll. Top with sliced onions. Place a slice of Provolone over the top of each sandwich. Return to the oven and heat until the cheese is melted, about 1 minute.

Season remaining juice with salt and pepper. Serve alongside the sandwich in individual bowls for dipping.