BMW factory driver Rossi finished runner-up in the second of the two GTWCE Sprint Cup races at the British venue aboard the WRT BMW M4 GT3 he shared with Maxime Martin.
Rossi, who is in his second full season of car racing after calling time on his two-wheel career, finished just under four seconds behind the winning Attempto-run Audi R8 LMS GT3 shared by Ricardo Feller and Mattia Drudi at the end of the one-hour race.
Martin started third in their BMW and pitted out of that position.
Rossi emerged from the tyre stops that followed a brief safety car period in second behind Drudi, who had moved up from sixth before the stops.
He initially had reigning champion and team-mate Charles Weerts on his tail in one of the WRT sister cars before establishing some breathing space.
Weerts, who shared his BMW with fellow three-time Sprint Cup champion Dries Vanthoor, came back at Rossi in the closing stages, taking the chequered flag just 0.8s behind.
Martin and Rossi benefitted from problems encountered by the two Audis that ran 1-2 in the early stages.
Source: Autosport