After five wins from the first six rounds, the Swans have been well beaten by top-four contenders Geelong and the Western Bulldogs in the past fortnight.
The Swans' losses have coincided with a considerable drop in their ability to win the clearances, which has been a hallmark of Roos' team for much of the past decade.
With the prospect of novice ruck duo Mike Pyke and Jesse White doing battle against reigning All-Australian Aaron Sandilands, Roos said the likes of Brett Kirk, Ryan O'Keefe, Jude Bolton and Josh Kennedy would need to improve their output at the stoppages.
"Watching most teams against Fremantle, you know you're not going to get your hand on the ball in the ruck contests. It's just the reality," Roos said on Monday.
"I thought our ruckmen were competitive in the hit-outs on the weekend; we just got badly beaten at ground level at certain stages within the game.
"The main area of concern is when the ball hits the deck. Wherever the ball goes, we need to get there before the Freo boys do."
Roos reiterated his belief that his side wasn't good enough to mix it with the competition's best unless it was absolutely at full strength.
With Daniel Bradshaw, Craig Bolton, Ben McGlynn, Jarred Moore, Mark Seaby and Shane Mumford all absent against the Bulldogs, the Swans clearly have their concerns with personnel.
But with the exception of the two ruckmen, the core of the Swans' midfield group remains intact and Roos expected they would improve against Fremantle at the SCG on Saturday afternoon.
"We're just not getting enough of the football against the two best teams in the competition and Freo have been really good in that area as well," he said.
"Everything else tends to flow from that; it doesn't matter whether it's our team or other teams. That's certainly an area of concern for us, given we were so good at that in the first six weeks and in the last couple, we've dropped off significantly.
"I'm sure our midfield would be disappointed because we've got some experienced guys in there and they've got enough pride in their performance to really bounce back this week in that area."
Roos confirmed that Bradshaw was likely to return for Saturday's game, while McGlynn (quad) was still a 50-50 chance to line up against Freo.
