Pat the roast dry, and season all sides with salt and pepper.
Heat a large pot over medium heat with a drizzle of oil. Add the roast, and sprinkle onions around the outside. Sear the roast, about 5 minutes per side, on all sides.
Move the roast and onions to a slow cooker. Add the carrots, celery, garlic, sage, thyme, rosemary, black peppercorns, and beef broth. Cook on low for 8-10 hours, or until fork tender. (Or on high for 5-6 hours)
Shred the beef, and add the bbq sauce. Serve on rolls with some lettuce, onions, and your favorite toppings.