Coach Richard Kerr-Bell's side, with an average age of about 17, did not expect to achieve much this season, as a mass player exodus left the Sunnyvale side looking short of numbers and experience.
Yet the youngsters had posted warning to others with a spirited match against University the week before, and on Saturday they continued with no respect for their elders to move off the bottom of the Football South Premier league, above Northern.
Roslyn appeared complacent, and should have taken heed when Island striker Max Johnston twice hit the home side's woodwork, and goalkeeper Tom Stevens had to make several good saves.
However, keeper Steven's mobility was a factor in the first goal, when indecisive defence created a muddle, a rebound and a grateful strike by Matt Milton into the empty Roslyn net for a 1-0 lead.
Only three minutes later, substitute James Govan threaded his shot through a defensive crowd to equalise, and a few decent passing sequences gave Roslyn supporters some hope.
But as referee Calvin Berg reached for his final whistle, an early cross from Tom Milton flew over the Roslyn defence and Holdridge judged his run, jump and header superbly, to bullet the ball past keeper Stevens and into Roslyn's net.
Kerr-Bell pointed out his side's resilience after two early big defeats this season.
"Our average age is around 17, and they acquitted themselves well. Our man of the match was Stewart Catto.''
Roslyn coach Colin Thom was still shell-shocked, but praised Green Island and expressed his dismay at the "comedy of errors, that led to the first goal''.
"But their winner was a top header,'' he said.
Caversham continued to cruise over the FPL horizon with a controlled 3-0 win over coach Lewis Houghton's revamped Northern side.
Caversham coach Tim Horner as usual appreciated the value of a clean sheet.
His side has not conceded a single goal in the four matches played so far.
The usual suspects struck for Caversham, a Tore Waechter header and precise shot by Mitchel Carter gave a 2-0 score at halftime, and, with 15 minutes to go, a classic left foot drive by Lewis Jackson earned the final result.
At the Caledonian Ground, Dunedin Technical looked set for a rout of Varsity, scoring almost from the kick-off, when Tim McLennan netted, then regular goals had Alistair Rickerby (2) and Sam French join in for a 4-0 halftime scoreline.
But coach Darren Hart's student side climbed back in the second spell, harnessing a tailwind.
First Truthus Toheriri scored, then Elliott Martin chipped in and spectators leaned forward sensing some drama.
However, despite playing clever passing football, the student curse of too many touches allowed Technical to play sound defensive football and ride out the potential storm.
Mosgiel, which had the bye, remains second, six points behind Caversham, and Technical remains equal third, just ahead of University.
In the women's senior competition, University dished out Dunedin Technical's first defeat for some time with a sound 4-1 win at Tahuna Park.
Technical pressured an early "own goal'' then University's Rachel Christie equalised, and a strong second half earned the students their win.
At Logan Park, Roslyn-Wakari beat the University B team 3-0, with goals from Una Madden, Alex McIntosh and Jordyn Walker.
