Salt and Pepper both sides of the roast. On the stove top, sear the beef rump roast on all sides.
Place roast in 4 qt or larger crock-pot.
Add soup and onions to the crock-pot.
Cover and Cook on LOW for 8 hours or until the meat is fork tender.
In a bowl, mix the butter, parmesan cheese and the garlic powder. Spread the butter on the rolls and toast butter side up in the oven.
Remove the roast from the crock-pot and slice thinly. Return the meat to the crock-pot.
Add a slice of cheese to the inside of the buns and spoon in meat on top of the cheese (optional). Serve with a side of the extra juices for dipping.