Aidan Connolly and Ross Callachan got the vital goals to pull them ten points clear of Morton with six games to go and a trip to Cappielow beckoning on Saturday.
They took the lead in 22 minutes on the counter attack when they broke quickly following a Saints corner after a concerted spell of pressure by the Paisley side.
Callachan supplied the killer pass, playing in Connolly whose pace took him clear into the area and he produced a great finish to beat the unprotected Jamie Langfield.
Callachan then put the Fife side two ahead nine minutes before half-time and it was a personal disaster for Saints centre-back Jack Baird.
The young defender tried to head Louis Longridge’s deep ball back to Langfield but only succeeded in knocking it into the path of the Rovers midfielder who could hardly believe his luck as he shot home from close range.
Aberdeen boss Derek McInnes was there to watch loanee Lawrence Shankland but it was Alex Cooper, son of former Dons midfielder Neale, who hauled Saints back into the game two minutes before half-time.
He took a pass from Gary Irvine and cut in from the left to drive a low right-foot shot past Kevin Cuthbert.
There was a needless flashpoint in 65 minutes when Rae was sent to the stand for something he said to Barry Cook after the referee came across to have words with David Farrell who had been complaining about a free-kick.
Shankland might have earned a draw 11 minutes from time but missed the target from ten yards.