can you use it in werewolf form ?

You sadly cannot. You will be without unstoppable for a lot of the time.

How come a lot of druids run with bulwark and its get magnified when they are werewolves?

Oh i was thinking you meant specifically with grizzly rage using tempest roar.
You can still use the armor that permanently makes you a werewolf or regular skills with tempest roar and be wolf and use earthen bulwark.

What are you trying to accomplish?

Yeah running lighting with grizzly rage. Have deliberating roar aspect, can use it as dr source. But unstoppable or control braking only coming from grizzly rage