Room service is available but they have hours of operation. The menu in the room should indicate what times they serve hot food, and the menu will show a list of items that are available 24 hours a day. If you can't find the times, you can ask the front desk.
Remember that if you use these premium services, you should tip. Also remember that you might not know they are helping you. For example, when you check in, a person might ask if you need help with your bags. If you say yes, then you are using the bellman services. So remember to tip if you do. If you don't want to tip, you don't have to, but it is a little rude. Finally, if you don't want any help, just tell them, "No thank you."