Green’s Dictionary of Slang

1. an uproarious joke.

1896		Ade Artie (1963) 25: ‘There’s no need of makin’ a roar,’ said the stranger, with a conciliating smile.
1948		(con. 1944) N. Mailer Naked and Dead 93: What a roar that had been.

2. a complaint.

1896		H. Blossom Checkers 25: Because he dropped a couple of ‘bones’ [...] he made a roar that’s echoing still.
1905		H. Green Actors’ Boarding House (1906) 82: Never saw one yet who wasn’t making a roar about sumpin’.
1913		H.G. Van Campen ‘Queen of the Slack Wire’ in McClure’s Mag. Jan. 319/1: You needn’t be afraid of this little lady makin’ a roar to the old man.
1931		Irwin Amer. Tramp and Und. Sl. 160: Roar.–A protest or complaint, especially when against some criminal act or against a tramp’s actions or mere presence.
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 179/2: Roar, n. Any obstreperous protest; testimony against an accomplice.
1962		Ragen & Finston World’s Toughest Prison 815: roar – A protest or complaint.