I’m not 100% sure I understand the question. 
 

A Sonos speaker can be in a single ‘system’ at a time. Similarly, a Sonos speaker can be in one Sonos ‘room/zone’ at a time. 

Are the Era’s part of a surround “room”, serving as rear speakers? If so, you could unbond them and set them up as separate “rooms” (but as part of the same system). You will lose any Trueplay settings on the surround room.

Yes they share a surround system with a beam gen 2 and a Sub mini. That’s the case, I don’t want to lose the surround system by unbonding the Eras. 

You can’t.  They can either be configured as surrounds, as a stereo pair, or as their own separate rooms.  This is because the configuration of each takes a reconfiguration of the radios (in the case of normal to surrounds and surrounds to normal) and various handshakes to get right.  It’s not just a simple switch.