Pat the beef chuck roast dry with paper towels.
In a small bowl, mix together salt, black pepper, garlic powder, and onion powder.
Rub the seasoning mixture evenly all over the beef roast.
Heat olive oil in a large skillet over medium-high heat.
Sear the beef roast on all sides until browned, about 3-4 minutes per side.
Transfer the seared roast to the slow cooker.
In a bowl, combine beef broth, Worcestershire sauce, dried thyme, and dried rosemary.
Pour the broth mixture over the roast in the slow cooker.
Cover and cook on low for 8 hours, or until the beef is very tender and easily shredded.
Remove the roast from the slow cooker and shred the beef using two forks.
Strain the cooking liquid into a saucepan and simmer over medium heat until slightly reduced, about 10 minutes, to make the au jus.
To assemble each sandwich, place a generous amount of shredded beef on the bottom half of a sandwich roll.
Top the beef with one slice of provolone cheese.
Place the sandwich under a broiler or in a toaster oven until the cheese melts, about 2-3 minutes.
Serve the hot roast beef sandwiches with a small bowl of the warm au jus for dipping.