Steamship Round is the Beef Round with the Rump taken off. Taking the Rump off makes it cheaper, and lets it sit upright on the bigger end for easy carving. Still, even with the Rump off, a Steamship Round will weigh in between 30 and 50 pounds (13.5 to 22.5 kg.) They are used in buffets at restaurants, institutions, in armed forces canteens, and by caterers to feed large groups at events such as weddings and conventions.
You have to specially order Steamship Round from a butcher.
The official name for this cut is: "Beef Round, Rump and Shank Partially Off, Handle On."
Allow about 5 hours at 300 degrees F (150 C). Then, let rest covered out of oven for 2 hours before serving. This will let the centre finish cooking, and will let the juices rise back out to the outside edges, so that outside slices don't dry.
To carve, first trim off any excess fat, then cut thin slices to the bone across the grain.