Only six trades were made during the AFL's trade period earlier this month after what Roos termed a week of frustration.
The issue continues to trouble the AFL Players' Association (AFLPA), which is pushing for free agency and has been given until the end of December to devise a model for consideration by the AFL Commission.
Swans forward Ryan O'Keefe, who unsuccessfully sought a trade back to Melbourne and has now said he will re-sign with the Swans, also called for free agency for veteran players.
"I'm sure the AFL will be frustrated that only five players changed clubs (there were six trades in total)," Roos said.
"There's probably some concern from the players' association in terms of free agency.
"It is a frustrating and difficult week. As an industry we need to look at it."
But Roos added: "Free agency is dangerous.
"What happened in America in the NFL system when free agency came in is all the good players made all the money.
"If I was advising the players' association or (AFLPA chief) Brendon Gale I think that's the biggest problem with free agency.
"Buddy Franklin, Barry Hall, Adam Goodes get well paid. But they'll get an exorbitant amount of money to leave clubs and what will happen is players who are good to very good players will start to take huge pay cuts and that's what has happened in the NFL.
"So I'm not a massive fan of free agency but I certainly think there needs to be a think tank in regards to trade week.
"There's a lot of wasted time, there's a lot of one-upmanship and teams trying to get it over other teams and the old win-win (deal is a thing of the past)."
Roos said only three or four clubs were good to deal with and keen to arrange a fair trade.
"A lot of clubs are just looking to get what's best for them and not what's best for anyone else. It is frustrating but I'm not sure free agency is the answer to it," he said.
"With a couple of drafts coming up that are going to have less and less of the better players because of the new clubs (Gold Coast 2011 and western Sydney 2012) coming in, in this particular draft ... no one wanted to give away first-round draft picks.
"So it will be interesting to see what happens over the next two or three years with the new clubs coming in."
Gale said last week the players' association felt its members deserved greater rights of self-determination.
The players' boss says free agency will give an out-of-contract footballer the right to avoid trade week and the pre-season draft and negotiate his next contract directly with any club, providing he has served a minimum number of years.
