Green’s Dictionary of Slang

1. (US prison) the last night of a prison sentence [one wakes up, rolls out of bed, and the sentence is over].

1918		H. Simon ‘Prison Dict.’ in AS VIII:3 (1933) 31/1: ROLL-OVER. The night before one’s release, implying that one tosses about but doesn’t sleep then. The full formula was Ten (for example) more days, a roll-over and a get-up. [Ibid.] 32/2: TURN-OVER. Roll-over.
1927		H. Yenne ‘Prison Lingo’ in AS II:6 281: Roll over, or a get up — The last night before being released.
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 180/2: Roll-over. (P) The last night’s sleep of a prison term.

2. (US Und.) a confession; a plea of guilty [roll over v. (1)].

1986

C. Stroud Close Pursuit (1988) 215: His public defender managed to plea-bargain the manslaughter charges away in exchange for a rollover on the felony assault.

3. one who presents no problems, e.g. to a policeman, a ‘pushover’.

1986

J. Ellroy Suicide Hill 33: ‘This is too fucking sad. Anybody this fucking crazy has gotta be a rollover’.

4. (US und.) an act of betrayal, informing.

2005

R. Cea No Lights, No Sirens 251: He was an outside hire by the Shah to clip him for the rollover, just like you said.