If I remember correctly, the only enchants you can recover from robes are the "+Magicka Regen" and "Reduced spell cost and magicka regen" (depending on the school of magic ie destruction/illusion) enchants
When I disenchanted a +150% regen, I wasn't able to re-enchant the full 150% onto my chest, the highest I could get it was 40%
There are three types of enchants that you can get from robes. The first is a straight up magicka regen, with the base regen values as 20%. The second is a fortify magic school enchantment which reduces the cost of a spell school. The base value for this is 8%. The last one is a combined fortify magic skill and magicka regen, where the fortify base value is 5% and the magicka regen is 10%. I think the magicka regen portion of this enchant may be fixed though.