Mourinho's side went into their Europa Conference League clash in Norway as the heavy favourites.
But an upset looked on the cards when Bodo/Glimt led 2-1 at half-time.
The hosts then amazingly scored four times in 26 minutes in what was a quite incredible result.
Roma's travelling fans, understandably, were not happy at all.
The Italian club's players were confronted by the angry away supporters following the humiliation.
Mourinho was also extremely upset. That was the first time in his career that a team managed by him had conceded six goals in a game, after all.
He spoke to the media following the final whistle and he took the blame for the poor result.
“I decided to play with this line-up, so the responsibility is mine,” he told Sky Sport Italia.
“I did it with good intentions, to give an opportunity to those who work hard and to rotate the squad on a synthetic pitch in cold weather. I decided to rest many players."
Mourinho then couldn't resist having a go at his players.
“We lost against a team that showed more quality on the night. It’s that simple," he continued.
“If I could always play with the same XI, then I would. It’s risky, because we have a huge gap in quality between the two groups of players.
"I knew the limits of this squad, it is not new to me, but I still expected a better response. As I said, it’s my choice to play them, so my responsibility.
“I never disguised the fact we were a squad with real limitations. We have 13 players who represent one team, the others are on a different level.
“At least the positive thing from now on is that nobody will ask me why I always use the same players.”
Ouch. Can't imagine that the Roma players that featured on the night will be pleased with that...
Mourinho and Roma will be looking to get back on track when they play against Napoli on Sunday.News Now - Sport News