In a scrappy affair, the first chance of note fell to the visitors, with Rory Gaffney unlucky to see his goalbound shot cleared to safety by Killian Brennan in the fifth minute.
Opportunities arose at the opposite end as the half progressed, with Craig Sives heading narrowly wide from a Gary McCabe cross in the 13th minute while Gary O’Neill wasted a glorious chance five minutes later, crashing over the crossbar from McCabe’s delightful centre five minutes later.
There was little incident of note to enliven the paltry crowd up to the break, with Gaffney powering a drive that forced a routine stop by Oscar Jansson in the 37th minute while McCabe shot wastefully at Barry Ryan when well placed a minute later.
After Sives was fortunate to escape with a handball in the 47th minute, Rovers took the lead midway through the half when Daryl Kavanagh’s shot was only parried by Ryan into the path of O’Donnell who was rewarded for his perseverance by slotting home.
Limerick’s chances were effectively ended when substitute Paudie Quinn was red-carded in the 77th minute, two minutes after his introduction.
SHAMROCK ROVERS: Jansson; Gilbert, Sives, Gartland, Powell; McCabe (McCormack, 90), Rice, Brennan (O’Donnell, 60), Dennehy; O’Neill (Kavanagh, 54), Twigg.
LIMERICK: Ryan; Kelly, Purcell, Guthrie (Daly, 82), S Treacy; C Treacy, O’Leary, McGann, Coughlan (Bradley, 69), McGrath (Quinn, 75); Gaffney.
Referee: Anthony Buttimer (Cork).