Room Observer

The room observer components allows actors to be notified whenever any actor enters or exits a room.
The components bind themselves to the Room Level's On Actor Enter Room and On Actor Exit Room delegates and then call their own On Actor Enter Room and On Actor Exit Room delegates.
Thus, once placed on an actor, you just have to bind to the component delegates to be notified when those events occur.
Only actors that don't ignore the Room Object Type collision channel will trigger the events.

Room Observer Component

Place this component on your actors if they can move between rooms or are not placed in room levels.

This component implements the Room Visitor interface to detect whenever the actor enters/exits room to bind automatically to the delegates. So, the actor with this component needs to be setup to overlap with the Room Object Type collision channel.

Static Room Observer Component

Use this one if your actors will never get out of their room and are placed in room levels.

This component will bind to its parent level at Begin Play and unbind at End Play automatically. It has much less overhead than the non-static Room Observer component. Thus, it makes a good choice when you have lot of actors that need this feature and are static to their room.

How to use it

Just add the component on any actor, and then bind to its delegate the way you want.

Here a simple example of a "fog of war" actor that will hide/show itself when the player enters/exits its room. It is an actor placed directly in the room level and will never move to another room, so I attached a Static Room Observer on it.