When using Wwise with Unity, you need to use the AkBoxEnvironement component and AkAuxSendAware component together.
AkBoxEnvironement replaces the "reverb zone". AkAuxSendAware has to be added to the object being affected by the reverb. And finally, you must define your reverb effect in Wwise, as a Effect Shareset. You can read about the Aux Send concept in our Wwise doc (F1 in Authoring) and in the Wwise SDK doc for programmers (probably in C:\Program Files\Audiokinetic\Wwise\SDK\Help). Look for the function SetGameObjectAuxSendValues. You can also look at the AkBoxEnvironement and AkAuxSendAware script code to understand how it is used.