Season the beef roast with the salt and pepper. Heat 1 tablespoon oil in a large skillet over medium-high heat. Add the roast to the skillet and cook for 4 to 6 minutes on both sides, or until well browned. Transfer to a 4 or 5-quart slow cooker.
Add the onion, pepperoncini, Italian seasoning and garlic to the slow cooker. Pour the beef stock over the roast and cook on the low heat setting for 8 to 10 hours, or until the meat is meltingly tender.
Transfer meat to a cutting board. Skim off as much fat as possible from the cooking liquid in the slow cooker. Using 2 forks, pull the meat apart into bite-sized pieces.
In a large skillet, heat remaining 1 teaspoon oil over medium heat. Add the sliced red bell peppers and sauté until softened, about 6 minutes. Remove from the heat.
To make the sandwiches: Divide the meat between the 6 rolls and top with some of the sautéed peppers and the giardiniera. Serve with some of the liquid on the side for dipping. (If you don't mind a messier sandwich, add the meat back to the liquid after pulling it apart. Spoon the meat onto the rolls, making sure to get plenty of juice in the process. The roll will be soaked, and juice will drip down your arms when you eat it, but that's a good thing, right?)
