Shields of reflection can not be worn together with robes.
The shield of reflection has no randomized appearence and can be identified at sight. The effect of reflection makes it a beneficial asset ta any character — even if only used occasionally.
Since a shield of reflection is too large to be worn together with a robe any spellcaster should look for alternative body armor like leather suits, studded leather suits or crystal armour suits. Bear in mind that you loose magic regeneration when you discard your robe!