The user might be looking for a complete description or analysis of a specific film they believe exists. Since it doesn't, I should clarify that there's no known film titled "L'Enfer de Mario Salieri" from 1999 directed by or featuring Monica Roccasanta. Instead, I can provide information on "Amadeus" and suggest clarifying the details if they have another film in mind. Also, maybe they meant a different title or a different year. Let me frame the response to address the confusion and provide the relevant information about Salieri and the known film about him.