Is there an administrator in each room during a call?

There is no concept of an administrator.

The management of calls in a room is within the scope of business management layer, which can be implemented by customers through their own signaling layer, calling SDK interfaces (startPublishingStream/stopPublishingStream/startPlayingStream/stopPlayingStream) to implement call management. Or use the SDK's signaling service for related notifications. For details, please refer to Real-time Messaging and Signaling.