The Dees showed some fight early on at Darwin's TIO Stadium but could never mount a serious challenge after Freo booted seven of the first eight goals.
Fremantle dominated the key stats, with a whopping 61-32 inside 50 advantage, and Melbourne continually shot itself in the foot with some poor skill errors.
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Roos could cop the mistakes as the humidity rose and the football became slippery, but refused to blame the conditions for the turnovers early in the match.
"The first half was the story, at times, of our season where we just cough the ball up so easily and they prey on turnovers better than any team in the competition," Roos said.
"You have to do everything right to be able to beat them. It says a lot about where they're at and for our guys it's a real wake-up call to how far away we are from being anywhere near as good as that."
Among the skill errors, Roos lamented two set shots missed by Chris Dawes and co-captain Jack Grimes in the second quarter that would have put the Dees ahead.
"You have to take your chances, you can't miss goals from the top of the goal square," he said.
"At one stage it should have been three-all. Dawes misses, Grimes misses and it's three-all and mentally you're still in the game.
"You miss them and it's six (goals to) one at half-time."
Melbourne only booted four goals but Roos thought the match was far from the Demons' worst performance for the year.
"Oh, no, no, not by a long way. I think for us, we got a lesson from a really good team," he said.
"They're a Grand Final team from last year and we're a 17th team from last year.
"They're such a difficult team to beat. We constantly see them, they're just such a competitive team and they do the basic things well.
"They're going to be there at the end of the year, right in the thick of it."
Melbourne slumped to 16th on the ladder following its 11th loss this season and faces a tough clash against Geelong at the MCG on Saturday.
