Roma were ordered to close the Curva Sud section of the Stadio Olimpico where their most dedicated fans sit because of racist chants aimed at AC Milan striker Mario Balotelli during Monday's 2-2 Serie A draw at the San Siro.
A disciplinary tribunal said Roma supporters chanted "The red-and-blacks are a team of blacks", referring to the colours of the Milan shirt, and persistently booed Balotelli when he had the ball.
The tribunal said the game, which ended 4-2 to the home side, was marred by verbally offensive chants.
The ruling means Inter will play Sunday's derby with city rivals AC Milan without the support of hardcore fans who usually sit in the Curva Nord.
Italian soccer authorities have cracked down on discriminatory as well as racist chanting this season, announcing automatic stadium closures as a penalty.
This has angered many fans who have long traded insults. Ultras from teams including Naples have campaigned against the rules.