Rotherham dominated to begin with, forcing Torquay on to the back foot and Ben Pringle shot just over after 23 minutes. Two minutes later Kayode Odejayi broke through on a solo run and smacked a shot against the upright.
The visitors could have had a goal after 18 minutes when Rene Howe robbed Nicky Hunt, but he couldn't find a team-mate with his cross and Ian Sharps put the ball behind for a corner.
The breakthrough came in the 34th minute following a real mix-up in the Torquay defence. Kevin Nicholson's attempted header back to his goalkeeper went straight up in the air and, after the defender failed to clear at the second attempt, Alex Revell gratefully turned it into the empty net.
Rotherham should have had a second three minutes after the break but Odejayi blasted over with the goal at his mercy and then had another effort blocked on the line.
And Rotherham were almost made to pay for the missed chances with 10 minutes to go when substitute Niall Thompson picked out Billy Bodin, only for him to blaze the chance high and wide.