Rojas had yet to score for Sydney but her haul ensured the Sky Blues remain four points clear of second-placed Melbourne City.

Ally Green bagged the second goal of her ALW career when she looped a speculative shot from the touchline over the head of Canberra goalkeeper Keeley Richards.

Princess Ibini and Rachel Lowe rounded out the scoring late in the piece at Kogarah Oval.

The defeat means Canberra are now winless in their past eight games -- stretching bck to last season -- and apart from an early spell they did little to trouble the hosts who were without without Matildas duo Remy Siemsen and Cortnee Vine.

"We've always lost players to internationals and injuries so I was confident in the players who could come in and do the job," Sydney coach Ante Juric said.

"Rojas is a different player to Remy and Cortnee who have played for us for so long that they're like a machine.

"Rojas came up with the goals so that was really pleasing for us."

Rather fortuitously, Sydney opened the scoring in the 28th minute when Rojas tumbled to ground in the box under very light attention from Canberra fullback Hayley-Taylor Young.

Referee Isabelle Blaess pointed to the spot and Canberra had every right to feel aggrieved with the decision, especially when Rojas converted with ease.

Just before halftime Rojas was in on the action again, intercepting a bobbling Lauren Keir backpass and chipping the ball over Richards to put Sydney two up before the break.

Canberra had few opportunities to hit back but when one did it present itself captain Michelle Heyman was only able to fire limply at Sydney goalkeeper Jada Whyman.

With Sydney's defence almost impenetrable, Whyman has hardly been troubled all season and she has not conceded a goal since their opening-sround win over Newcastle.

One of those defenders is left back Green who showed she could have an impact at the other end of the field when she played a neat one-two with Mackenzie Hawkesby after a throw-in and then curled over Richards from the touchline.

Rojas poked in her third after the ball fell into her path from a corner before being given an early mark.

Ibini avoided Chloe Middleton's challenge to finish with 10 minutes to go and Lowe followed up on the act to make it six.

"It's a bit upsetting, we wanted to come here and give it to Sydney," Heyman said.

"It's really frustrating. We are just not finding our feet.

"We need to go back to the drawing board and change something."

Australian Associated Press