Tempest Roar is a Druid Unique Helm that makes your Storm Skills Werewolf Skills. Like all Unique items they provide a powerful effect that can't be found on any other item. These effects can't be moved around like Legendary Aspects resulting in limited flexibility when incorporating them into your build.
How to Obtain - Random Drop
Rarity - Rare
Tempest Roar Mechanics
Many Unique items change the way skills and builds work in significant ways.
Your base Storm Skills gain the Werewolf tag, allowing you to use them when in Werewolf Form, including with Dire Wolf's Aspect.
For further information, see our Build Guides & Unique Item Wiki
Tempest Roar