Place the Eye of Round Roast in the bottom of a slow cooker.
Cut the butter into 4 pieces and place around the roast.
Pour the pepperoncini's in their juice over top of the roast and then sprinkle with Ranch mix and au jus mix. Stir the seasonings into the liquid. Sprinkle the entire thing with black pepper.
Cook on low for 6 hours.
Add the carrots, onions, potato, and celery around the sides of the beef roast. Cook for an additional 2 hours.