Irish secured a bonus point, for scoring four tries, inside the opening half hour, but Doncaster could have been closer than 26-10 adrift at half-time and bagged the only try of the second period, seven minutes from time.
Knights made a positive start, but the Exiles struck after eight minutes when their forwards drove over the line and Blair Cowan touched down from the lineout following the visitors’ first penalty.
Ben Meehan landed the first of an eventual three conversions, hitting a post from almost in front with his failed attempt.
Kurt Morath replied with a penalty, but pacy wing Benjamin Loader sliced through for Irish’s second try on 16 minutes.
Early in the second quarter home No 8 Joshua Tyrell broke up the middle from a lineout in Doncaster’s half and Tom James was in support to score a reviving try which Morath converted.
Doncaster’s Elliott Creed had an opportunity from the only scrum of the first half, on 25 minutes, but Doncaster were penalised and Fergus Mulchrone went over following the resulting lineout.
Another lineout led to Irish’s fourth try, scored by Motu Matuu, but Curtis Wilson and Cameron Cowell both had chances to cut the deficit just before the interval.
There was no further scoring until the 73rd minute when Cowell and Wilson carried Doncaster into Irish’s 22 and then play was moved left and Creed sent Richard Hayes in for a try which Stephen McColl improved, but late pressure could not produce another score which would have secured a deserved bonus point.