[3] For many years, Connolly was a frequent contributor of verse and short stories to national magazines; in 1928 he served on the first board of directors of the Catholic Book Club.

In a 1951 interview with Pilot which was the official publication of the Archdiocese of Boston, "Connolly recalled that he wrote much of the magazine himself in the middle of the night, sometimes using pseudonyms for various articles".

When the Catholic Church in Mexico was persecuted during the imposition of Calles Law and Knights of Columbus leadership spoke out against the Mexican government as well as against the silence of the U.S. government, Columbia editor Connolly boldly produced a November 1926 issue cover with Knights carrying banners declaring "Liberty" and "The Red Peril of Mexico".

[5][6] Mary Connolly Breiner eventually left consecrated religious life to marry and work as a psychologist.

Capra followed Roscoe's lead in describing the writer/producer from Boston as "a hulking, 230-pound, six-three, black-haired, blue-eyed gum-chewing Irishman with the mien of a dyspeptic water buffalo".

Connolly died following complications from open-heart surgery at St. John's Hospital in Santa Monica, California in 1964 at the age of 66 years.

In a 2017 interview with Kathryn Jean Lopez of the online news magazine Crux Now, Mirarchi explained that Mr. Blue did not sell very well when it was first published.

When Dorothy Day and her work lifting up the poor with the Catholic Worker Movement began, however, "Americans started to see that there really were people like Blue in the world; he wasn't just some fanciful ideal".

Screenwriting credits include The Right to Romance (1933), Palm Springs (1936), Youth Takes a Fling (1938), and the Charles Vidor film Hans Christian Andersen (1952).

Connolly co-wrote the Ann Sothern-Lew Ayres film Maisie Was a Lady (1941), with Elizabeth (Betty) Reinhardt.

[22] Connolly is also credited with co-writer Jean Holloway as Screenwriter for the 1946 MGM film, Till the Clouds Roll By.