Green’s Dictionary of Slang

rosey n.

(US gay) the buttocks, the rectum.

1972		B. Rodgers Queens’ Vernacular 24: posterior [...] rosey (fr colloq rosey red cheeks: ‘Here’s a posey for your rosey’ accompanied, usually by the extended middle finger).
1989–2003		R.O. Scott Gay Sl. Dict. 🌐.

In exclamations

up someone’s rosey!

(US) an excl. of aggressive dismissal.

1963

in T.I. Rubin Sweet Daddy 12: Screw ’em. Up their roseys.