One of my favorite cooks is Prime Rib. It's really best on a Roti w/ a temp probe to keep it med-rare. I LOVE a lot of smoke in everything/anything that I cook, so for me hickory wood chunks on the coals for the duration is a major concern. In the US, used Roti's go for $50 to $150 on CL. Don't know about the Australian version of CL.
IMHO, get the Roti for your charcoal cookers.
SJ