I know the bread itself is certified kosher, and I can never get over how inexpensive it is at Costco.
Was in the store (Brooklyn), looking at it. An employee approached me and told me the bread is kosher, but once they unwrap it and bake it they can't vouch for it since the bread is baked in their non kosher ovens.
She offered to bring me out frozen packages of the bread so I can bake it at home. (They arrive at Costco par baked)
I had one of the rolls today and its really good!