You plain and simple don't know the rules if you think that wasn't roughing the passer. He had control of the arm that hit Roethlisberger in the head, regardless of whether or not he was held. And a hold would not negate a personal foul anyway. Krig is right that he'll probably be fined.
The Steelers were playing with two undrafted rookies in the secondary, including one that is a safety, at cornerback, so I don't know how much I can really complain. It's unfortunate that Roethlisberger got picked by Carr at the end, but the reality is that this is not the game that matters for the Steelers. It's next week that matters.
Both the Giants and Steelers control their playoff destiny. If they win their last two games, they're guaranteed a wildcard, and both can still win their divisions with help.