Reaper of Souls First Look: The Mystic
http://us.battle.net//d3/en/blog/11337855
With Enchanting, you will be able to reroll one property on a Rare or Legendary item simply by speaking to Myriam, opening up her Enchant menu, and then paying a material cost. It's that easy!
While not all properties can be rerolled, most can, and you'll be able to reroll a single property over and over again, as many times as you like. This allows Enchanting to feel meaningful, while still allowing lots of room for you to hunt for even better base items (which, of course, you can then Enchant into even more powerful items, and so on).
Since the resulting property you receive during Enchanting will be random, it's possible that the new properties you're provided may end up being less desirable to you than the one you are replacing. But fear not! In order to mitigate this type of buyer's remorse, Myriam will also offer the previous property in the list of options when using Enchanting. So if you don't like the new property that Enchanting offered you, you can always choose to keep the old one.
Keep in mind that when choosing which property you wish to reroll, you will only be able to reroll that one property from then on out. After a single property has been changed via Enchanting, all other properties will become "locked in" and cannot be rerolled. Also, once you Enchant an item, it will become bound to your account and can no longer be traded to other players.