St George Illawarra coach Wayne Bennett admits he's yet to grasp a full understanding of his newly-acquired squad and says positions are up for grabs during the club's three NRL pre-season games.

Bennett, who crossed to the Dragons at the end of last season after 21 years at the helm of Brisbane, will coach his new club for the first time in Saturday night's pre-season clash with the Sydney Roosters in Perth.

The Dragons are also scheduled to play trial games against the Bulldogs and South Sydney and Bennett says the next three weeks are crucial as he contemplates his best line-up for their season-opener against the Melbourne Storm.

"I suppose the next three weeks, for me personally, I need to see them play to get a better handle on some issues with them," Bennett said in Perth on Friday.

"The only way I'll be able to do that is by them playing, so from my point of view the trials are a little bit more important than they have been in the past.

"I'm not trying to put too much pressure on our players and I want them to treat them as trials, but I need to see them play.

"I've got ideas about who's going to do what.

"Some positions are up for grabs but I haven't gone around and made general statements about that ... there are some opportunities there and they have a chance to grab them over the next couple of weeks."

The Dragons have named a strong team to face the Roosters, with former internationals Matt Cooper and Wendell Sailor in the starting line-up.

But Bennett warned not to expect a flawless performance from the side in his first game in charge.

"It's not all about one trial game and we are not playing a grand final tomorrow night, are we clear on that?" Bennett said.

"So we have got three games, we'll use the three games to get ourselves what we think is the best team and get those little areas of the game that you need to have working together."

Bennett, who led Brisbane to six premierships, said he was confident of bringing success to the Dragons.

"I'm confident we can improve on what they've done there," Bennett said.

"They've had some wonderful teams there and for whatever reason it hasn't fallen their way.

"But that was in the past."

Roosters coach Brad Fittler, eager to test the depth of his squad, has named an inexperienced line-up against the Dragons.

"It's going to be really interesting for us tomorrow night," Fittler said.

"From our point of view ... we've got our starter pack just about out."

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