What looked like a last-minute equaliser for the Plainsmen by Cody Brook to rescue a share of the points was nullified by an even later winner from Roslyn's Ben O'Farrell as he calmly floated the ball goalwards from 30m to clinch the win in added time.
Roslyn coach Colin Thom made six changes to his team line-up after last week's limp loss to Green Island at Ellis Park.
Supporters reached for team sheets to identify new goalkeeper Sam Jewel, centreback Tom Bealin, defender Jack Kirkwood, striker James Govan, Nathan Wilkie, from the reserves, Rupert Mark back from injury and, most memorable, striker Tennessee Kinghorn, who celebrated his elevation to first-team football with two goals against Mosgiel.
"We needed a shake-up after last week,'' coach Thom said.
"The lads showed their appetite from the kick-off, taking the game to Mosgiel in front of their home support.''
"Young Kinghorn grabbed his chances with two well taken goals to give us a 2-0 lead at the break to earn our man of the match award.''
But Mosgiel showed its class and resilience by clawing back into the game and, despite being without Chilean midfield playmaker Eder Franchini, the plainsmen hit back with a goal from striker Callum Flaws, who transferred midweek from Caversham.
Mosgiel's shares dipped again midway in the second spell when centreback Tom Cairns received a second yellow card from referee Andrea Verolino, and the Queenstown-based defender headed for an early shower.
Despite being reduced to 10 men, Mosgiel subbed on Cody Brook who has been plagued by injury, and the coach's son obliged with a well taken header that seemed to have rescued a point.
But young O'Farrell capped an exciting week - he captained the Kavanagh College futsal team to a national championship win recently - and was calmness personified as he laced in the late winner for Roslyn.
At the Caledonian Ground, Northern was expected to man the barricades against a powerful Dunedin Technical side, but took the initiative in early exchanges and was unlucky not go ahead.
Unluckier yet was a penalty awarded for hand ball by referee Calvin Berg, and Technical's big Scottish striker Sam French hit an ice-cool spot kick to beat Northern keeper Fred Haidekker in the 30th minute.
The award frustrated Northern's coach Lewis Houghton, and things got worse as Technical striker Alistair Rickerby scored the first of his two goals on a quick counter-attack.
"We struggled a bit after going behind, but still had a ‘goal' chalked off for a marginal offside, and had some good spells of pressure in Tech's goalmouth,'' Houghton said.
Technical coach Tony Martin admitted his side was a bit disjointed, but he was pleased with the clean sheet and also with youngsters Ben Allan, Tom Petersen, Liam Watson and striker George McCall, who got on the scoresheet.
"But it was the best that Alistair [Rickerby] has played for a while, and by also scoring two goals, he was clearly our man of the match,'' Martin said.
Green Island continued its good form but struggled to make an impact on Caversham, as coach Tim Horner's big red machine bulldozed onwards at Tonga Park with a 4-0 result and goals from Mike Hogan, Tore Waechter, Ben Wade and, inevitably, Lewis Jackson.
Almost as intimidating as the steady scoring is the seemingly impregnable defence which has yet to concede a goal in this season's five matches.
In the Women's Premier League, the rampant University Women's side secured a 4-0 win over Dunedin Technical Maroon thanks to goals from Mary-Ann Cant, Renee Bacon, with two, and Rachel Christie.
At Ellis Park, Dunedin Technical grabbed a two-minute lead when Lara Wall scored, but for the second week running Roslyn-Wakari's Una Madden hammered in a spectacular goal to equalise at 1-1.
