To slice the roast, make several slices (1/2 inch to 1 inch thick) from outside of the roast toward the rib bone. Cut along the inner side of the rib bone to loosen each slice.
At the meat market, you can ask the butcher to cut between the bone and the meat, and then tie it back together. This way, you can still roast the meat with the bone but slicing the meat is easier.