With Balmain Ryde leading 26-24 with little time left, Ropati's four-pointer gave the Vodafone Auckland Lions a critical victory.
It came in a match in which they revealed both sides of thier character.
They began the match brilliantly against the sixth-placed Tigers at Leichhardt Oval.
Powerhouse second rower Sonny Fai had his ninth try of the season in a matter of minutes, Steve Buckingham converting in his return from injury.
Balmain Ryde countered when first-grade fullback Shannon McDonnell went over for a converted try but that prefaced a period in which the Vodafone Auckland Lions were totally dominant.
First Fai made it 10 tries for the season and then winger Michael Crockett, who also has a great strike rate in the NRL, was on the scoresheet.
Soon enough fellow winger Malo Solomona was in as well for his eighth try of the year.
With Buckingham adding the extras, the Vodafone Auckland Lions were cooking at 24-6 at halftime.
But something went seriously amiss in the second spell as the Tigers roared back to 24-all with three converted tries of their own.
And when they went ahead 26-24 it seemed a cruel defeat faced the visiting side - but the Vodafone Auckland Lions rallied for Ropati to give the side hope of still making the top eight. Match details:
Balmain Ryde Tigers 26 (Shannon McDonnell 3, Tevita Metuisela tries; Ben Jeffery 4 conversions, penalty).
Vodafone Auckland Lions 28 (Sonny Fai 2, Michael Crockett, Malo Sololoma, Jerome Ropati tries; Steve Buckingham 4 conversions).
Halftime: 24-6 Vodafone Auckland Lions.Like