This will cause the primary room bot to send a message to the room. It will look like the bot is speaking to the room just as any other user would.
/as chan #chat message Hello, I'm a bot.
While this can be a fun way to liven up a room, talking bots are cute, you might want to be careful not to use this too often. When people see bots speak intelligently they may get confused about what a bot is and expect it to be able to speak like a person in general.