Crock-Pot French Dip Sandwiches

Season the roast with salt and pepper, set aside.
Heat the oil in a heavy cast iron skillet over medium-high heat. Add the roast to the pan. Sear the meat on both sides; about 3 minutes per side, or until the meat releases from the pan.
Remove the roast from the pan and place into a 6-quart slow cooker.
Add the onions into the same pan. Cook until lightly browned; about 5 minutes.
Add the broth, Worcestershire sauce, garlic, oregano and thyme to the pan of onions and season with salt and pepper to taste. Pour the onion mixture over the roast in the slow cooker. Cover and set the slow cooker on low for about 8 hours.
When the beef has cooked, preheat the oven to 350 degrees F.
Remove the beef from the slow cooker and let it rest on a carving board. Reserve the onions and broth.
Slice the rolls in half, horizontally, and place them cut side up onto a sheet pan. Lay 2 to 3 slices of cheese onto the rolls. Bake 5 minutes, or until the cheese has melted.
Divide the beef evenly into 4 portions. Place onto the cheese topped rolls. Then top with onions and place the top of the roll onto the prepared bottoms.
Secure with a toothpick and cut at an angle in half.
Ladle some of the broth through a sieve into ramekins for dipping.
Serve immediately.