Green’s Dictionary of Slang

roll in the hay n.

also roll-around, roll in the meadow, toss in the hay, tumble in the hay
[SE roll/tumble n. (2) + SE hay]
(orig. US)

1. sexual intercourse, with the implication of spontaneity, adultery or the open air.

[US]B. Schulberg What Makes Sammy Run? (1992) 197: Hell, this isn’t a roll in the hay for me, there’s plenty of that around.
[UK]S. Jackson Indiscreet Guide to Soho 56: An agent’s license [...] is worth far too much to be risked for a tumble in the metropolitan hay.
[US]N. Algren ‘Watch Out for Daddy’ in Entrapment (2009) 122: The evil town-boys had only to name some country boy like he’d had a roll-in-the-meadow with me and Daddy would whup that boy.
[US]R. Chandler Long Good-Bye 8: It might have been a hotel room rented for a meeting or a farewell, for a few drinks and a talk, for a roll in the hay.
[US]W. Styron Set This House on Fire 204: So it’s lowbrow diddling [...] A cheap smelly roll in the hay.
[US]B. Rodgers Queens’ Vernacular 173: roll-around an instance of coitus; a roll in the hay.
[US]K. Vacha Quiet Fire 115: A toss in the hay does not make for a relationship.
[US]R. Campbell Wizard of La-La Land (1999) 16: Looking for a tumble in the hay with the bitch goddess Success.
[US]Mad mag. Feb. 14: It’s like a slept with Martin Sheen and then took a roll in the hay with Woody Allen.
[Aus]T. Spicer Good Girl Stripped Bare 50: ‘Hey, luv. Feel like going for a roll,’ asks a guy wearing a ‘wife beater’.

2. a person viewed as a possible sexual partner.

[US]E. Hunter Blackboard Jungle 180: If a girl uses that word, she knows damn well what she’s saying, and you can chalk up another roll in the hay.