Chasing a target of 114 for victory, RoI completed the task in 67 minutes, scoring 115 for one this morning.
Captain Wasim Jaffer, who was batting on 25 when stumps were drawn yesterday, did not take to the ground today because of an injury.
Gambhir, in his 109-minute innings, enthralled by hitting 11 boundaries.
Robin Uthappa, who came in instead of Jaffer, supported him from the other end, crawling to 18 in 56 minutes and facing 34 balls before being dismissed by Praveen Kumar.
RoI had paved the way for their victory yesterday itself, winding up the UP second innings for 166 in 245 minutes after taking a lead of 65 runs. Set a target of 114 for victory, RoI were comfortably placed at 45 for no loss at the end of the second day's play. As expected, the victory today turned out to be a mere formality.
The game saw 31 wickets falling for 630 runs, including 17 on the first day and 13 on the second.
Brief Scores: UP 148 and 166 lost to Rest of India 201 and 115 for 1 (Gautam Gambhir 64 not out, Robin Uthappa 18; Praveen Kumar 1 for 50)