Yep! Silvers can also be roan. My Lonesome, who is a true bay roan, is out of a true roan silver bay mare, Mhoon's Fine Sugar. I think she's registered as a red roan, but I know the mare and she is absolutely silver bay roan.
And then my silver pinto mare has sabino roaning. Not true roan, but a roan... If that makes sense.