Green’s Dictionary of Slang

1. the bed; thus hit the Roberta, to go to bed [sack n. (4)].

1992		R. Puxley Cockney Rabbit.
2002		Pete’s Aussie Sl. Home Page 🌐 Roberta Flack: the sack, the bed, e.g. ‘hit the Roberta’.

2. dismissal from one’s job [sack n. (2a)].

1983

R. Aven-Bray Ridgey-Didge Oz Jack Lang 41: Roberta Flack Sack (fired from job).