De Rosa's business flourished from 1918 to 1929, particularly during the Roaring Twenties, but it largely declined during the Great Depression.

Toward the end of World War II he was reported to be back in New York and beginning to work on post-war theatre projects, just before his death.

While he was a small child, his parents emigrated to the United States, arriving through Ellis Island and settling in New York City, where they were living by 1898.

[3] By 1919 he was in a partnership called "De Rosa & Pereira", and that year he represented several clients in appeals against decisions of the superintendent of buildings of the City of New York.

He spent some years in London and settled for a while in Naples, where in 1935 he was reported to be "wonderfully helpful" to American and English visitors.

[1] Before or during the World War II, De Rosa returned to New York City, where by 1944 he was working on new theatre projects.