We had Concierge service on the Voyager and I assume it is the same on the Radiance. The Concierge Lounge is accessible by a special key which will be in your room when you arrive on the ship. They have pastries and such in the morning for breakfast and special coffees all day. From 5 to 8 each evening they have an open bar and hors'douves. In addition the Concierge can arrange reservations in the special restaurants and well as help with shore excursions and any in cabin entertaining you might do. They were quite helpful to us.
The room is available to suite and Diamond members 24/7 as a getaway or for a quick cup of specialty coffee (automatic machine). Concierge will have hours he/she is in attendance and that is when the extra goodies are available.