Holders Wigan may be in the Championship this season, but they upset Premier League opposition for the second time in less than a month in the cup on Saturday.
After beating Crystal Palace to reach the last 16, first-half goals from Chris McCann and Ben Watson helped Rosler's men to a 2-1 win at Cardiff City.
Inclement weather harmed Wigan's preparation for the game, Rosler revealed afterwards, but despite nine hours of travelling on Friday, they were fresh enough to claim a big away win.
Rosler told the club's official website: "Our performance was fantastic, particularly after the troubles we had in getting down here for the game.
"We had to go through an unbelievable journey down after our flight was cancelled yesterday afternoon.
"We only arrived at the hotel at 10pm to 10.30pm and we had been travelling from more or less 1pm.
"The players were magnificent today despite all that we went through, and they have shown real pride in their performance.
"The quality we showed was very impressive, we didn't get to train much between our last game and this one, but with experienced players like we have, we always know what we are capable of."
Rosler added that goal hero Watson - who has now scored in three of his last four FA Cup appearances, including the winner against Manchester City in last year's final - had sustained an injury, leading to his substitution just before the hour-mark.
"We've lost Ben for Tuesday's game (against Barnsley in the league) after he picked up a knock," he added.
"We were forced to make the change and up until then his performance had very pleasing with a magnificent goal to put us back ahead."
