The Swans will take just 24 players to Narrandera to face North Melbourne in their final NAB Challenge match on Friday as they fine-tune their preparation for their season opener against the Saints on March 27.
Barring any injuries, Roos said his round one team would be comprised of the players who will play on Friday, with the addition of recuperating full forward Daniel Bradshaw (knee).
With the majority of his experienced senior players fit and firing, the Swans coach said the final positions would come down how each player matched up against the Saints.
"There may be some guys who may be playing a little bit better than some of the guys who [will] play [in round one], but you have to be aware of the opposition and what you need," Roos said.
"If Daniel does come in, obviously he takes a spot deep in the forward line and that might cost someone who does play that role.
"The good thing is we're healthy, we're pretty fit and we've got a good team that is in good form playing against the Kangas in Narrandera."
Bradshaw continued to train with the rehab group on Wednesday afternoon, but Roos said he intended to name the former Brisbane Lion for the clash against St Kilda.
"It's hard to put a percentage term on it but I expect him to play," he said.
"The only reason he wouldn't play is if something happens between now and March 27.
"At this stage, we've pencilled him in to play but having said that, if something happens with just a bit of a hiccup or he gets some swelling from a session then he won't play."
Potential debutants Lewis Jetta and Gary Rohan are among those sweating on a round one berth and Roos said the pair remained a strong chance of donning the red and white at ANZ Stadium on March 27.
The two first-round draftees have played all of the Swans' pre-season games and Roos conceded that their heavy workload was an issue that needed to be carefully managed.
"Probably less with Lewis because he's come from a senior competition but certainly Gary; we've been talking to him this week about how he's feeling, but you'd imagine the kid's not going to tell you he's feeling tired knowing that he's a chance to play in round one," he said.
"We're certainly aware of that and that's why we're backing them off a little bit during the week.
"Sure, they don't want to be backed off on Friday night but it's something you're aware of, not just this week but going through the course of the season as well."
Daniel Bradshaw is a $310,100 forward in this year’s Toyota AFL Dream Team.
Gary Rohan is a $137,500 forward/midfielder.
