Hello Patrick,
There is a permission Conversation > Call > Monitor.
As well, you can use the Default Role Supervisor which already has this permission.
If you want more details you can look to help.mypurecloud.com, I have paste the related link below.
https://help.mypurecloud.com/articles/products-roles-and-permissions-list/
Laurent
------------------------------
Laurent Pret
Genesys - Employees
------------------------------