Parramatta has upset defending premiers Sydney Roosters to join last season's wooden-spooners Newcastle in the NRLW grand final.

The Eels had snuck into the semifinals with their only win of the season last week over the Brisbane Broncos and were given no chance against the previously undefeated Roosters at Lang Park on Sunday.

But they were never headed in a stunning 24-10 victory.

Earlier, the Knights' high-profile recruits Tamika Upton and Millie Boyle powered their side to victory.

Fullback Upton scored twice, while prop and captain Boyle produced a spectacular solo try in the 30-6 defeat of last season's grand finalists St George Illawarra.

Parramatta's win will make for a sea of blue and gold at Sydney's Olympic stadium next Sunday with the NRLW decider the curtain raiser to the NRL's Eels-Panthers showdown.

Inspired displays by Eels halves Ashleigh Quinlan and Tayla Preston — behind a ferocious and resolute pack — laid a foundation of success for the Dean Widders-coached side.

Quinlan scored herself with a light-stepping move and put centre Abbi Church over to give the Eels a 12-4 half-time lead.

Halfback Preston was enormous and charged like a forward at times.

She chased hooker's Brooke Anderson kick to score after the break and then put up a trademark bomb for Rikeya Horne to seal the deal.

The Roosters were well off their game and bombed two certain tries with winger Leianne Tufuga and centre Isabelle Kelly dropping balls with the line wide open.

Those mistakes were a result of the blowtorch applied by the Eels' middle forwards Simaima Taufa and Kennedy Cherrington.

Knights through to premiership decider

Former Broncos pair Upton and Boyle starred on their old turf at Lang Park in the first match of Sunday's double-header.

They played a key role in rebooting the Knights, who lost all five matches in their debut season.

The Dragons trailed 12-6 when star fullback Emma Tonegato crossed in the right corner, only for the on-field decision to be overruled after a knock-on.

The Dragons dominated territory in the second half, but the Knights' defence held firm.

Upton breezed through for her second try before winger Kiana Takairangi's crossed to ice the cake.

AAP