The Swans trailed by 26 points at quarter time and never really got much closer as Fremantle recorded its first win of 2009.
Roos was disappointed that his team started slowly and then the lack of firepower up forward hurt the Swans' chances of bridging the gap.
Star defender Craig Bolton was also playing his 150th match for the club, but it was captain Kirk's milestone the Swans desperately wanted to win for.
"One of the main disappointments for the night was that we couldn’t win for Kirky,” Roos said.
“He was the one that had to put us on his shoulders again and some of the guys would be disappointed in their performance based on what Brett has given the footy club.
"He had to rally the troops again and it was disappointing we didn’t win for his milestone.
“A lot of the guys owed it to Brett to fly the flag better than we did, particularly in the first half."
Roos knew Fremantle would come out firing after a horror start to the season and a tough week off the field and hopes his young players learn from the experience of what an opposition under pressure can produce.
"They were a club under siege and you generally expect an effort like that in those circumstances,” he said.
“It was a credit to them that they came out ready to play after four weeks of disappointing results. They got out early and we couldn’t peg them back.
"Four our young players, it would be their first experience of playing a team that was 0-4 and coming off an 80-point loss.
“They need to learn that teams fluctuate and you know that if you are Brett Kirk or Jude Bolton, but if you are Brett Meredith, Jesse White, Kristin Thornton, Craig Bird or Kieren Jack you need to see to learn from it.
“That's the big thing from the game."
Along with Kirk, Jude Bolton and only a handful of others, Roos was delighted with the game of Ryan O'Keefe, who was carrying a heavy load without key forwards Barry Hall and Michael O'Loughlin.
"I thought he was outstanding. His work rate is phenomenal and he was one of three or four guys who played really hard tough footy for the whole game," he said.
"He works so hard and was really tired by the end. He had a good battle with (Steven) Dodd, but 'Pebbles' was one of our better players and it was a good effort as it's hard for him at the moment without Hally and Mick.
"Our forward line wasn’t the reason we were behind, but it was why we couldn’t peg back a seven goal lead, because we didn’t have enough raw talent up there for someone to kick five or six in the second half."
The Swans will now look to bounce back against Richmond at the SCG on Sunday and Roos is confident both his star forwards will be available.
"I expect Hally to play next week, but obviously we've been over here for a few days and aren’t too sure how his rehab is going," he said.
“Mick played in the seconds but I'm not sure on his game time or how he went. Hopefully he got game time into him, feels good, and can come in next week as well."
