Create a chat (Send DM). Search the user by his Balagur username. Or type a full Balagur address: @user:balagur.online.
Rooms main purpose is to serve 3+ users. It doesn't allow direct voice calls, but offers on-demand join group rooms for video, audio and screensharing. Direct messages (1-1 chats), instead allow regular voice calls as well as creating a video conference room.