The only moment of excitement in a disappointing first half came in added time when Paul Wotton''s deflected shot was brilliant saved by Rotherham goalkeeper Rhys Taylor.
With both teams simply hoofing the ball over the top and running after it, chances were at a premium. For Rotherham, Alex Revell headed wide from Sam Wood''s cross after 20 minutes and then Danny Harrison and Danny Schofield both shot over the bar.
For Plymouth, their only other threat was an audacious effort by Maxime Blanchard from his own half which had Taylor back-peddling, but the ball bounced once, cleared everyone and went onto the roof of the net.
Nine minutes into the second half Lewis Grabban''s cheeky lob almost deceived Jake Cole in the Argyle goal.
The deadlock was finally broken with 20 minutes remaining when substitute Gareth Evans beat Darren Purse for pace but was upended in the box and Grabban netted his 17th goal of the season from the spot.