Roos was disappointed with his team's lack of intensity against the Bombers in a must-win game for the Swans.
He was at a loss to explain the performance but said the rest of the season offered an opportunity for player development which he intended to take.
"It was disappointing given the stakes," Roos said.
"We just didn't have the usual intensity against a team we know is young and fit and uses the ball well.
"We hung in and hung in but we really didn't give ourselves a chance to win. It was probably our worst performance over the last five weeks.
"We just looked off the pace today, they all looked pretty tired today and our better players just didn't play great.
"We didn't have any class players today."
The Swans' ninth loss of the season has them two wins plus percentage out of the eight.
With games against St Kilda and Geelong coming up in the remainder of the season, an appearance in the finals seems a very long shot.
"If you're talking about finals, you'd be unlikely to play in them this year," Roos said.
"You expect this point to come at some stage; you're just not sure when it's going to come.
"But it's an opportunity for the club to take over the next six or seven weeks. In a positive sense it could be a good opportunity."
Roos hinted some of the more established members of his senior squad could be forced to make way to give the next generation valuable experience.
One player who could get a run is Gold Coast youngster Jesse White, who booted 11 goals for the Swans reserves on Saturday as a full forward, backing up after eight last week.
Roos revealed flu was the reason White was not selected in the senior squad, but he should be an inclusion against Carlton next week.
The coach also praised the performances of Heath Grundy and rookie Mike Pyke, a late replacement for Jarrad McVeigh.
McVeigh's complained of hamstring soreness in the pre-game warm-up and was withdrawn from the team as a precautionary measure.
Canadian 25-year-old Pyke ended with 10 possessions and 15 hit-outs.
"Pykey has clearly improved a lot. His effort today was pretty good," Roos said.
