The home side were a man down with 24 minutes gone when centre-back Marc Joseph received a red card for a professional foul on Kyle Perry.
But even against 10 men, Vale failed to push men forward and home goalkeeper David Stockdale had only one save to make before the break, a comfortable take from Perry’s shot.
The best chance of a goal came at the other end a minute before the sending off when Jamie Green pulled back a perfect cross from the left but the ball went between Richie Barker’s feet when it only wanted turning into the net.
Even after the break, there was little in the way of adventure from Vale and it was 10-man Rotherham who took the lead after 67 minutes with a goal from substitute Drewe Broughton.
Ian Sharps’ long punt out of defence bounced over the last defender and Broughton nipped in to lift a shot over Joe Anyon and into the corner of the net.