That is correct. Just have the bot type anything in the channel you need the room-id for.
We could technically do this all automatically, write this to a var, like %roomid. < key > .channel and call this in our resub.
Instead of the room-id == [ ID HERE ] it would be room-id == %room.id
I'd have to write the code though to do it all automatically. But here's the thing, i wouldn't want to process the on * event all the time, as i only need the room ID once.
Better to just grab it once, instead of writing the ID to a var.