The ex-Tallaght favourites scored in either half to put a huge dent in Rovers’ title ambitions.
Manager Pat Fenlon admitted that the trip to Co Louth was a must-win for his side if they were to remain in the title race. However, following last night’s result, Rovers now trail Stephen Kenny’s side by 15 points.
That leaves Cork City as Dundalk’s nearest challengers in the remaining seven matches.
The table-toppers made the breakthrough on 15 minutes, when Ronan Finn robbed Gary McCabe of possession in midfield before receiving the ball back from David McMillan at the edge of the box to rifle low to the bottom corner. It was only his third league goal of the season but it was his second against Rovers this year.
The visitors did dominate after that and a Brandon Miele shot on 28 minutes that had to be clawed around the post by Gary Rogers was their only real chance of note.
Having weathered the storm, Dundalk then made sure of the win in the 68th minute when Gannon charged up the right to get on the end of McMillan’s pass before slotting to the bottom left hand corner.
Rogers; Gannon, Gartland, Boyle, Massey; Mountney (Meenan 67) O’Donnell, Towell, Horgan; Finn (Shields 62); McMillan (Kilduff 74).
Murphy; Madden, Kenna, Webster, Byrne; G Brennan, McCabe (Cregg 75), Blanchard (R Brennan 85), Miele (McCaffrey 76); Drennan; North.
P McLaughlin (Monaghan).