The agents you get through RCCL work for RCCL and therefore they do not get commission. Outside travel agents are able to book cruises for the same price as the RCCL agents but they still get a commission from RCCL for the booking.
So, no, the RCCL agent would not be able to give you anything for booking direct.
Also note that with RCCL, every time you call them you get "the next available agent" and may never work with the same person twice.
Other lines (like Carnival) allow the agents to "own" an account and they will call you with specials and you can contact them directly. RCCL is different that way.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007