The visitors had previously enjoyed an unbeaten start to the league but they received a rude awakening within four minutes as Billy Dennehy was upended by Dean Delany, who was sent off. Gary Twigg fired his penalty past replacement goalkeeper Paul Skinner for his fourth league goal of the campaign.
Although Philip Hughes was narrowly wide with a 25-yard free-kick minutes later, there was little doubting the title holders’ supremacy and their lead was doubled in bizarre fashion on the half hour as Stephen Hurley’s backpass rolled untouched to the net with, replacement goalkeeper Paul Skinner 30 yards from his goal.
Suitably disheartened, the visitors retreated in an exercise of damage limitation but there was little they could do to defend a stunning Ronan Finn strike, which stung Skinner’s hands en route to the top right-hand corner, entering injury time.
The hosts resumed in a similar vein with Finn hitting the upright within three minutes of the restart, although Shelbourne should have narrowed the deficit when Paddy Kavanagh was denied by a sprawling save from Oscar Jansson, following Conan Byrne’s through ball.
At the opposite end, Shelbourne’s defensive generosity was emphasised by the concession of a fourth goal, with Ian Ryan’s poor header pounced on by Aaron Greene. The only sour note for the champions was sending off of substitute Gary McCabe, who received two yellow cards, the second for diving in the 83rd minute.
SHAMROCK ROVERS: Jansson, Gannon, Oman (Gartland, 46), Sives, Brennan; Dennehy (McCabe, 62), Rice, Finn, Turner, Greene; Twigg (Kavanagh, 75).
SHELBOURNE: Delany; Matthews, Ryan, Boyle (Paisley, 81), Fitzgerald; McGill, (Skinner, 6), Cronin, Hurley, Byrne (Murphy, 62); Kavanagh, Hughes.
Referee: T Connolly (Dublin)