In all there were five tries for the Exiles as the Titans slumped to their seventh defeat in seven Zurich Premiership outings.
But for Irish, it was a highly successful afternoon and means that they move to fifth place in the Premiership table, just a single point between South East rivals Wasps.
The scoreline perhaps flatters London Irish, in that the Titans did not give up for the duration of the match, with fly-half Jason Strange in excellent form with the boot and the pack gaining a fair amount of possession.
But with Mark Mapletoft putting in another excellent performance for the Irish, the Exiles were able to put plenty of distance between them and their opponents.
Mapletoft finished the match with a personal tally of 15 points, with his replacement Barry Everitt also having a successful run-out to score a try, two conversions and a penalty.
For London Irish:Tries: Bishop, Everitt, Horak 2, SackeyCons: Mapletoft 3, Everitt 2Pens: Mapletoft 2, EverittDrop-goal: Mapletoft
For Rotherham Titans:Tries: Elliott, BensonCons: Strange 2Pens: Strange 4