if you delete a rogue system and it shows back up, it is usually a sign that the MAC address is broadcasting and it is being picked by a Rogue System Sensor.
But going into the detected system and clicking delete is the way to do it.
You might be able to just mark them as exceptions.
Looking at the English ePO 4.6 product Guide see Chapter 21 - Detecting Rogue systems.
look for the section 'Adding systems to the Exceptions list' (around page 276)
yeah i would add it as an exception if you anticipate that you will see it again on your network.... itll just keep showing up.
If it keeps showing up it's still broadcasting.