Mail room is debatable. It is becoming more and more acceptable to use it as one word. If you type in mailroom into a sentence and ask for spell check you will get a misspell.
It is one word. Hope this Helps!
"Fitting room" is typically written as two words.
Two words. It is a room of the press.
It is two separate words: jury room.
Living Room is 2 words.
Fanbase is one word in the in the United Kingdom, but may differ elsewhere
No it is two words: post room.
Both. Bath=room= bathroom bath and room are two different words it is a compound word
"Classroom" is typically written as one word.
two words, locker room
Food service is two words. An example sentence is "the food service is good here".
Ballroom is one word meaning a large room used for dancing.
As in "the layout of the room is very nice", it is one word. As in "I will lay out all the pens on the table", it is two words.