As of early 2019 Carnival no longer has completely free room service.
There is a menu of salads, sandwiches and desserts which are completely free during the day, plus additonal hot food selections are available for a small fee.
Late-night menu options (after 10:00PM to 6:00AM) are also available for a small fee.
Room Service MenusView / Download Room Service Menus
*** It is customary to tip when your room service arrives. ***