Season the beef chuck roast evenly with salt and black pepper on all sides.
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 beef to the slow cooker.
Add the sliced onion and minced garlic on top of the beef in the slow cooker.
In a bowl, whisk together beef broth, soy sauce, Worcestershire sauce, dried thyme, and dried rosemary.
Pour the broth mixture over the beef and onions in the slow cooker.
Cover and cook on low for 8 hours, or until the beef is very tender and easily shredded with a fork.
Remove the beef from the slow cooker and place on a cutting board. Use two forks to shred the beef into bite-sized pieces.
Strain the cooking liquid through a fine mesh sieve into a bowl to remove solids. Reserve the au jus for dipping.
Return the shredded beef to the slow cooker and stir to coat with some of the reserved au jus.
Preheat the oven broiler.
Place the sandwich rolls on a baking sheet, top the bottom halves with shredded beef and a slice of provolone cheese.
Broil the sandwiches for 2-3 minutes, or until the cheese is melted and bubbly.
Top with the roll tops and serve immediately with warm au jus on the side for dipping.