How do I rename an EM-COP Incident Room?

You are not able to rename a custom EM-COP Incident Room once it has been created. 

Rooms remain active and can not be archived.  If you really need to change the Room name, then you might consider creating a new custom Room with the correct name.  In the other Room you could place a text box with a message indicating this room is not being used and direct users to the correct one.