Green’s Dictionary of Slang

1. (US black) 50 cents.

1941

D. Burley N.Y. Amsterdam Star-News 2 Aug. 13: The old Lenox Avenue hotbeds where you knock a pad for a double-rough.

2. (US prison/Und.) a 50-year jail sentence.

1971–2

C. Shafer ‘Catheads [...] and Cho-Cho Sticks’ in Abernethy Bounty of Texas (1990) 203: double rough, n. – a fifty-year sentence.