"We have a few things to improve and one of them is that we gave Roma too many chances at the start of the second half," he told Sky Sport Italia.
Guardiola recognised that the game was atypical after Bayern scored five goals in the first 35 minutes on their way to their European record away win which left them top of Group E with maximum points.
"This game is an exception, an incident," he said. "It's not the difference between the two teams, we will see that in two weeks. We got a quick goal and that relaxed us, then we got another. Rome are a team who always play well, but we were very aggressive, made the right decisions and found space."
His opposite number Rudi Garcia took responsibility for the disaster.
"It was a technical collapse, not a mental one," said the Frenchman.
“The first person to make a mistake was myself. I got the strategy wrong. In the second half, we showed some pride and would have scored more goals if it hadn't been for their goalkeeper.
“Bayern have showed that they are stronger than us. We were spectators at the match, we should have been more aggressive and compact," he added.
The Champions League captivated its continental audience with a record 40 goals in one eight-game night. Bayern, Chelsea, who beat Maribor 6-0, and Shakhtar, who enjoyed a 7-0 win at Bate Borisov, contributed 20 between them on an evening to forget for defenders and goalkeepers alike.
Players are not robots: Enrique
Barcelona manager Luis Enrique defended his side’s drop in form in the second half after Neymar and Lionel Messi maintained their lethal partnership with a goal apiece in a devastating first half as the Catalans swept aside Ajax 3-1 in Champions League Group F on Tuesday.
"We were very good in the first half and then we dropped off but this is logical because you can't play at that level for 90 minutes in every game," manager Luis Enrique told a news conference.
"The players are not robots. The idea is to reduce the number of errors and be as consistent as possible."
Ajax coach Frank de Boer, a former Barcelona player, felt his players let themselves down in the first half. "I was very angry at halftime because we can play a lot better and we did do a lot better afterwards," he said. "We are a young team with quality but we have to show that.”
City must do better: Kompany
Manchester City skipper Vincent Kompany said City have to get better if they are to qualify for the last 16 of the Champions League after stumbling to a 2-2 draw away to CSKA Moscow on Tuesday.
"It is always a matter of small margins in this competition," Kompany, who believed his side was denied a clear penalty in the first half, told reporters. "Obviously our first half was good and our second not so well.
“Things went against us that, for me, influenced the game in a way that was difficult for us. But we will look at ourselves and we know we have to win and we know it has to be better."
Results
CSKA 2-2 Man City
Roma 1-7 Bayern
Apoel 0-1 PSG
Barca 3-1 Ajax
Chelsea 6-0 Maribor
Schalke 4-3 Sporting
BATE 0-7 Shakhtar
Porto 2-1 Bilbao
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