The few incidents worthy of note for Saints came as the game neared the half-time break.
A 29th minute David Bagan run ended with the only save Colin Stewart had to make in the first 45 minutes.
Two minutes later, Peter McDonald lofted a pass through to Robert Sloan but Stewart beat the youngster to the ball.
Saints had survived an early scare with only six minutes on the clock but Craig Samson dived well to block a Sean Higgins drive.
The second half saw a transformed Ross County side snatch a quick lead in the 47th minute.
Centre-back Martin Canning nudged John Rankin's corner into the net with his shoulder.
Saints had no answer and fell further behind with 55 minutes gone.
Higgins stole the ball from under the noses of central defenders Kevin Rutkiewicz and Ian Maxwell and directed it towards the on rushing Steven McGarry.
McGarry was unopposed as he ran on to the ball to hammer it past the cruelly exposed young Saints keeper.
Samson prevented further embarrassment for the home side in the 74th minute when he made a spectacular save to finger-tip Alexander Burke's thunderous drive out for a corner.