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 roast to the slow cooker.
In the same skillet, add the sliced onion and cook for 3-4 minutes until softened. Add the minced garlic and cook for an additional 30 seconds until fragrant.
Transfer the onion and garlic mixture to the slow cooker, placing it on top of the beef roast.
Pour beef broth, soy sauce, and Worcestershire sauce over the roast. Sprinkle dried thyme and rosemary on top, then add the bay leaf.
Cover and cook on low for 8 hours, or until the beef is very tender and shreds easily.
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 saucepan to remove solids. Simmer the strained liquid over medium heat for 10 minutes to concentrate the flavors, adjusting seasoning if needed. This will be your au jus.
Preheat the oven broiler. Slice the French rolls horizontally but not all the way through.
Place shredded beef evenly inside each roll and top with a slice of provolone cheese.
Place sandwiches on a baking sheet and broil for 2-3 minutes, or until the cheese is melted and bubbly.
Serve the sandwiches hot with small bowls of warm au jus on the side for dipping.