Sydney Roosters remained on course to finish in the NRL top four by beating St George Illawarra Dragons, while Wests Tigers kept their finals hopes alive and dented those of Newcastle Knights.

The second-placed Roosters scored five unanswered tries in the first half at Kogarah Oval on Saturday and did not look back in a 34-12 triumph.

Victory moved them four points clear of Canberra Raiders – who face fifth-placed Manly Sea Eagles on Sunday – and South Sydney Rabbitohs in third and fourth respectively.

Joseph Manu barrelled his way through for the opener and Isaac Liu dabbed down a grubber kick before debutant Billy Smith finished off a fine move in the 15th minute.

Victor Radley and Daniel Tupou got in on the act ahead of half-time, the latter crossing in the left corner following an incredible switch of play from the boot of Cooper Cronk.

James Tedesco added a try of his own to a pair of assists from the first half, with scores from debutant Tristan Sailor – son of former Australia international and Queensland Maroons wing Wendell Sailor – and Luciano Leilua providing scant consolation for the Dragons.

Benji Marshall assisted four tries and David Nofoaluma grabbed his first NRL hat-trick as the Tigers thrashed the Knights 46-4 at Campbelltown Stadium.

Ryan Matterson touched down the opener after Marshall's grubber looped into the in-goal area and Robert Jennings crossed before Esan Marsters went through after a tremendous offload from Corey Thompson.

A brilliant no-look pass from Luke Brooks sent Luke Garner in and Nofoaluma got his first try following a lovely kick to the corner from Marshall, making it 30-0 at the break.

Nofoaluma chased down his own grubber to double his tally and completed his hat-trick after more sensational work from Brooks, with Michael Chee-Kam and Newcastle's Aidan Guerra exchanging scores late on.

The Tigers moved one point away from the playoffs, while the Knights are three adrift in 11th with two games remaining.