St George Illawarra is set to claim a historic NRLW minor premiership after fullback Emma Tonegato helped her team to a hard-fought 16-10 win over the Sydney Roosters.

The Dragons can seal top spot for the first time after Brisbane and Parramatta square off on Sunday, with the three-time champion Broncos needing to win by more than 20 points to edge ahead on points differential.

Saturday afternoon's loss at Kogarah means the Roosters sit fifth and must rely on the winless Newcastle beating Gold Coast on Sunday as well as points differential to play semi-finals.

Olympic gold medal-winning rugby sevens star Tonegato showed her footwork to score a second-half try against the Roosters, but earlier pulled off the tackle of the competition to keep her team in the lead.

Roosters speedster Jess Sergis made a break from 55 metres out but she was chased down by Tonegato, whose flying cover tackle took the centre into touch two metres from the tryline.

With both sides struggling to complete their sets in the first half, the Dragons' sole try was scored by PNG international Elsie Albert.

Prop Elsie Albert juggled a ball by Keeley Davis before getting it down in the ninth minute.

St George Illawarra's attack was not helped by losing centre Jaime Chapman to a head knock just three minutes into the match.

The Roosters had two tries disallowed by the bunker to remain scoreless in the opening stanza.

The Dragons scored two tries within two minutes early in the second half as Kody House ran a great line to collect a pass from five-eighth Taliah Fuimaono before Tonegato's try.

The lead was out to 12-0, with goal-kicking problematic for the Dragons, before Roosters prop Sarah Togatuki steam-rolled three defenders in the 47th minute.

Madison Bartlett again gave the Dragons some breathing space when the winger took an intercept and ran 65 metres to touch down.

And while Isabelle Kelly scored against her old side in the 69th minute, the Roosters lacked game awareness by attempting the conversion from the sideline rather than hunting another try before full-time.

AAP/ABC