Norwegian Ruud, a specialist on clay, dealt with flamboyant Darderi with the minimum of fuss, even after having to wait nearly two hours to restart a match he was already winning easily.
A huge downpour paused, but had no impact on, Ruud's march to his first final since winning in Stockholm in October last year.
When play was stopped, Ruud was 4-1 up and at advantage in game six of the first set, which he immediately won after the restart on centre court in Rome.
Not including the rain interruption Ruud took little more than an hour to see off Darderi to win a tour-leading 140th match on clay since the start of 2020, in which time he has won more tournaments on the surface than any other ATP player.
He enters the weekend not knowing who he'll face in the final, with further rain delays causing Jannik Sinner and Daniil Medvedev's clash to be suspended and taken into Saturday with the Italian a break up in the deciding set.