In a large skillet, heat olive oil over medium-high heat. Season the beef roast with salt and pepper. Sear the roast on all sides until browned, about 4-5 minutes per side. Remove from heat and set aside.
In the same skillet, add sliced onions and garlic, and sauté until the onions are soft and translucent, approximately 5 minutes.
Transfer the sautéed onions and garlic to the bottom of the slow cooker. Place the seared beef roast on top.
Pour in the beef broth, Worcestershire sauce, dried thyme, and an additional pinch of salt and pepper. Ensure the roast is submerged in the liquid.
Cover and cook on low for 8 hours, or on high for 4-5 hours, until the meat is tender and easily shredded with a fork.
Once cooked, remove the beef from the slow cooker and shred it using two forks. Return the shredded beef to the cooking liquid and stir to combine.
Preheat your oven to 350°F (175°C). Cut the French rolls in half and place them on a baking sheet. Toast in the oven for about 5 minutes, just until lightly golden.
Layer a portion of the shredded beef on the bottom half of each toasted roll. Top with a slice of provolone cheese and place the top half of the roll back on.
Optional - Return the sandwiches to the oven for an additional 3-5 minutes, or until the cheese is melted and bubbly.
Ladle some of the cooking liquid (au jus) into small bowls for dipping. Garnish the sandwiches with fresh parsley if desired.