Dragons coach Paul McGregor says discarded Origin halves Mitchell Pearce and James Maloney taught St George Illawarra a valuable lesson on Saturday night.

The ex-NSW pairing produced a relentless kicking display which was the platform for the reigning premiers' 30-22 victory.

The Roosters had just 45 per cent of the ball and the Dragons enjoyed a completion rate above 90 per cent but Pearce and Maloney's 16 kicks for a whopping 397 metres kept the Dragons on the back foot for most of the match.

McGregor said the polish on the end of the Roosters' sets was the difference in the game, as Dragons pair Gareth Widdop and Benji Marshall both had off nights with the boot.

"I thought we didn't win enough field position to win the game. We were coming out of our end a fair bit and their kicking game to ours was the difference between the win and the loss; simple as that," McGregor said.

"Their kicking game was relentless, putting it into one spot that had us starting our sets within 20 metres to our try line where we were erratic with our kicking game.

"At times we played too lateral and we didn't earn the right to.

"We tried to go around them before going through them but it just comes back to field position.

"You just can't win a game against a side like that without having field position."

Marshall put the Dragons back in the match with a brilliant solo try midway through the second half to cut the Roosters' lead to 24-16 but placed much of the blame for the loss on himself post-match.

"We did everything right that we wanted to, our forwards stood up against one of the best forward packs in the competition, but what let us down tonight was our last play options," Marshall said.

"Our kicking game was pretty terrible and it just gave them too many easy exits out of their half and with their forward pack you just can't do that.

"I think in the first half we were shifting off good go-forward whereas in the second half we were just going sideways off slow play-the-balls and they're too good a side for that.

"We were trying to build pressure and with that we were trying to put the ball in-goal and a couple rolled dead and you can't afford to give good teams seven tackles.

"I'm pretty disappointed about it and feel I let the team down a bit. It was disappointing but I thought against one of the best teams in comp we really stood up, and it's just a small thing we need to change to improve and I can control that next week."

The loss leaves the Dragons in 11th spot on 22 points, one win adrift of a four-team pack on 24, ahead of a crunch match with second-placed Penrith in Wollongong on Sunday.

"They played an outstanding game against the Bulldogs [on Friday], so we're going to have to match it," Marshall said.