“If”? I think Rosenstein was pretty clear, he defended the stonewalling as an artifact of their process and said they would continue the same process. Read between the lines, those documents are not coming anytime soon. He’s calling congress’ bluff. The worst they will do is censure him in a meaningless symbolic vote which Rosenstein will laugh off like Eric Holder did. He knows he has nothing to worry about from his lacky Sessions and frankly, even Trump will likely do nothing other than tweet about how disgraceful it is.
A censure would give Trump cover to fire him without running the charge of obstruction of justice. In fact it is Rosenstein who is the obstructionist.