Just a week after snubbing Roma to join Barcelona, Malcom scored against the Serie A side in a 4-2 defeat in Dallas.
Roma had announced they had reached a deal for the 21-year-old Brazilian, but the Bordeaux winger signed for the Spanish champions instead for £36.5m.
Malcom gave Barca a 2-1 lead, before Alessandro Florenzi, Bryan Cristante and Diego Perotti scored for Roma.
Earlier Stephan El Shaarawy had cancelled out Rafinha's sixth-minute opener.
The Italian club joked before the pre-season match that it had muted any mention of the player on Twitter.
Roma did not want to hear about Malcom before the game in Texas
And then Malcom scored
Roma were a lot happier on Wednesday morning after the win