Common loanword used in compounds like ルームサービス (room service) or ルームメイト (roommate), and sometimes as a standalone noun for a room in a building or facility.
I ordered room service at the hotel.
This room is spacious and comfortable.
tatami room; Japanese-style room
bathroom
room key
smoking room
non-smoking room
echo chamber
classroom
double room
twin room; double room
storage room; nonhabitable room; non-conforming bedroom