Green’s Dictionary of Slang

(US campus) a place where one can enjoy oneself in an uninhibited manner.

1967		W. Murray Sweet Ride 94: The second floor contained [...] some smaller romping rooms.
1985		Eble Campus Sl. Oct.
1996		Eble Sl. and Sociability 42: Alliteration marks [...] romper room ‘place to get rowdy.’.