Liam Boyce headed home the winner six minutes from time to seal a spirited win for the Dingwall side, who have now won seven and drawn one of their last eight games.
That run has taken County out of relegation danger and this latest win denied their opponents the chance to go fourth in the Scottish Premiership.
County were first to threaten as they were awarded a free-kick in a dangerous position when Simon Lappin unceremoniously brought down Martin Woods. Woods took the kick himself and curled the ball just wide of Saints ‘keeper Alan Mannus’ left-hand post.
At the other end David Wotherspoon flashed a shot across the face of the County goal.
But it was mostly County pressure early on and a Raffaele De Vita shot was blocked in front of goal by Steven Anderson. De Vita had another effort deflected behind for a corner as the home side went all out for an opener.
County captain Paul Quinn came to his side’s rescue in the 16th minute when he booted away a ball into the box, with Saints’ Michael O’Halloran in close attendance.
Boyce came agonisingly close to breaking the deadlock in the 78th minute when he ran on to a long ball, turned his marker and curled a ball just wide of the far post.
And the breakthrough finally came in the 84th minute when Jamie Reckord floated over a cross from the left and the hard-working Boyce directed his header inside Mannus’ right-hand post from eight yards.