Goa now have 16 points from eight matches while Assam, who gained only one point, failed to qualify for the knock-out stage as they finished third with 21 points from eight matches.
Resuming at their overnight score of 11 for no loss, Goa had put on 241/4 when play was called off by the umpires before the start of the mandatory overs.
Sagun Kamat fell early, caught by Roy off Ahmed for 11.
Rohan Belekar and A S Desai together put on 78 runs for the second wicket before Syed Mohammed bowled Belekar for 57.
Mohammed struck twice in quick succession to dismiss the dangerous Desai (40) and Manvinder Bisla (7) to claim three wickets.
All-rounder Regan Pinto, who grabbed two wickets yesterday, went on to complete a half century and remained unbeaten on 62 while sharing 75 runs for the fifth wicket with Ravikant Shukla, who remained unbeaten on 52.