This Weakaura will only be active in Molten Core and Blackwing Lair. While it's activated it will automatically roll on every Item according to your customized presets (Custom Options Tab).
You can change every preset to your liking and also add new items by item-ID with a roll preference under "Custom Item Rolls". Some custom rolls are already set i. e. for Runenloth, Major Healing Potion and Major Mana Potion.
Be careful when you reset the WeakAura to its default options your custom added items will be deleted!