If the meeting is being cloud recorded, it will only record the main meeting and none of the breakouts will be captured, regardless of what room the meeting host is in. It is currently only possible to record in breakout rooms with local recording.
The host must allow specific participants to record locally and it will only record the room the participant who is recording is in. Multiple participants can be given permission to record locally.
With local recording, the host may also enter a breakout room and their local recording will continue to record their experience once they leave the main room. However, anything that occurs before the host arrives in the breakout room will not be recorded.
References:
Zoom Help Center/Managing Breakout Rooms: https://support.zoom.us/hc/en-us/articles/206476313-Managing-Breakout-Rooms
Zoom Help Center/Cloud Recording Article: https://support.zoom.us/hc/en-us/articles/206185446-Cloud-Recording-with-Zoom-Rooms
Zoom Help Center/Local Recording Article: https://support.zoom.us/hc/en-us/articles/201362473-Local-recording