Place the oil in a skillet over medium-high heat. Season the roast with salt and pepper, brown on all sides, and then set in your slow cooker. Combine remaining ingredients in a bowl and pour over the roast. Cover and cook on the low setting for 8 hours, or until the meat is very tender. Remove the roast from the sauce and set on a plate. Tent with foil and let rest 10 minutes. Slice the roast, arrange on plates, top with the sauce and serve.