The Dublin side march on to the decider on May 14 at the Aviva Stadium, where they’ll meet the victor from the other semi-final between St Peter’s of Athlone and Pike Rovers, which will be replayed on April 20 at Leah Victoria Park in Tullamore following Saturday night’s abandonment due to adverse weather.
Sean Murphy put Sheriff ahead on 16 minutes when he guided his shot beyond goalkeeper Stephen Walsh.
Sheriff’s offside trap was breached when Nunan shot beyond Lee Murphy from eight yards.
The champions of 2012 and 2013 went back in front in the 25th minute when Kevin Lynch’s delightful deep free-kick from the right sailed all the way to Dunne at the back post and his close-range header made it 2-1.
Sheriff grabbed their third on 65 minutes. Sean Murphy’s cross was met by Rock, whose cutback was skillfully flicked into the net by Mark Higgins.
The Limerick side were unfortunate to see Shane Clarke’s header hacked off the line and were then hit by another swift Sheriff move for the fourth goal with two minutes left. Joe O’Neill fed sub Thomas Dunne and his low drive was turned in by the alert Rock from close-range.
L Murphy; P Murphy, Kavanagh, O’Neill, Lynch; Lester; Sean Murphy (Larkin 89), O’Brien, D Dunne, Higgins (T Dunne 83); Rock (Glen 89).
Walsh; Boyle, T Clarke, Hurley (Lynch 83), O’Mara (McMarlow 73); Hogan (Waters 59), Bradley, Harkin, Nunan; S Clarke, Tierney.