Sydney had trailed for the whole game and had to wait until Jude Bolton goaled from a free kick with little more than a minute left on the clock to steal the win.
Roos said his side was completely out-classed in the first half and it took a special effort from Brett Kirk and Adam Goodes to get the Swans back into the game.
"I just felt Woosha (Eagles coach John Worsfold) was obviously gearing up for a really big contest," he said.
"In the first half they just smashed us. So we were fortunate to get back in the game in the third quarter and gave ourselves a chance at least to get close.
"And then it always seems to come back to the last minute, minute-and-a-half."
Roos said despite trailing by 36 points at half time, the Swans believed they were still a chance to win if they could get back to basics.
"We were really poor at half time but they were very good and that’s what we talked about," Roos said.
"We had to put more pressure on them, we had to slow their ball use down, we had to play the game more on our terms and we were able to do that.
"I thought Goodes and Kirk were probably two that really just lifted the whole team.
"(Paul) Bevan finished up with two really critical goals, (Jarrad) McVeigh another couple of goals as well , so everyone seemed to get on board.
"But I think when you’re playing poorly like that you do need some senior guys to stand up [and] Kirk and Goodes were the two who really stood up."
Kirk kicked two vital goals late in the third quarter to get the Swans back in touch while Goodes recovered from a poor first half, in which he was reported for a head high bump on Adam Selwood, to finish with 21 influential possessions and eight marks.
Roos declined to comment on the possibility of losing Goodes through suspension but was enthusiastic about the imminent return of Barry Hall for next Saturday night’s clash against St Kilda.
"We’ll definitely play him, he’s in really good physical condition and he trained absolutely magnificently last week," Roos said.
"We’ll bring him back in and probably play him at full-forward, a bit of centre half-forward, but he’s in really good condition in terms of his fitness."He’s been working very hard."
