Related post on Meta SE: How do you delete a room on chat?
Related chat FAQ: Will these rooms exist forever?
Quote (emphasis mine):
Rooms will exist indefinitely, so long as there is at least one person actively talking in the room. A room is considered worth retaining if it has more than 15 messages by at least 2 users.
Rooms not worth retaining which are ...
Don't worry about it. Inactive rooms are deleted automatically by the system. I don't remember if non-mods can delete the rooms they created, but if you can, it will be on the "Access" tab.
So, try going to https://chat.stackexchange.com/rooms, find your room, click on the "info" link of the room, go to "access" and see if you ...