However the Roosters, who reached the NRLW grand final last season, were the favourites, with their squad chock full of Origin players and Kangaroos representatives.
The Warriors made a positive start, but couldn't convert possession and territory into points.
One try was called back (correctly) for a forward pass, and they lacked precision in their attacking sets early on.
The Roosters made them pay for their profligacy, when captain Simaima Taufa barged over in the ninth minute, after repeat sets on the Warriors line. The Warriors did well to repel several assaults, but the powerful Taufa was unstoppable from five metres out.
The Roosters dominated the first half, but couldn't extend their advantage, as the Warriors defended well, particularly on their right edge.
The Warriors got on the board four minutes before halftime, with Hale sneaking over from close range. It was good vision from hooker Krystal Rota, though the impetus had came from a superb 40-30 kick from Poko.
Kicking in general play was a major weakness for the Auckland side last year, and Poko looks a great signing.
She had strong day with the boot, often finding the grass with long range kicks that gave vital territory.
Poko is relatively new to league but has made a swift transition. She made her Kiwi Ferns debut in June, and will be a key figure for the Warriors this season.
She continued her impact in the second half, with more clever kicking, before a solo try as she over powered her opposite number close to the line, to break a 6-6 deadlock.
The Warriors went close again, with Onjeurlina Leiataua being held up over the line in a brilliant tackle by Kirra Dibb, before Atawhai Tupaea flashed over out wide to seal the win with eight minutes to play.
Tupaea, who recently returned to the sport after the birth of her son, finished off a lovely move, featuring a 1980s style double round executed at full pace.
Taufa scored her second on the hooter, though it was no more than a consolation try.
Warriors 16 (G Hale, C Poko, A Tupaea tries; A Nicholls 2 goals)
Roosters 12 (S Taufa 2 tries; K Dibb 2 goals)
Halftime: 6-6