Green’s Dictionary of Slang

1. the dole.

1939		J. Worby Spiv’s Progress 39: I’ve got about half a quid to see me through [...] I even went to the jam roll for a helping.
1986		R.G. Barrett Real Thing 127: I only go on the ‘jam roll’ every now and again.
1991		R.G. Barrett Between the Devlin 11: ‘I’ll [...] get on the jam roll’.
1997		N. Barlay Curvy Lovebox 83: Just go’a sort my jam roll.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.

2. (UK prison) parole.

1986		J. Campbell Gate Fever 16: Some of the prison vocabulary is simple rhyming slang [...] jam roll: parole, for example.
1995		J. Cameron Vinnie Got Blown Away 150: They don’t give jam roll people don’t eat or shit or talk. They like regular geezers, no danger to the community. Start shitting and talking you’re out automatic one year.
2000		J.J. Connolly Layer Cake 221: Getting a five, and with a drop of jam-roll getting out in three, is as much as I can get my head round.
2008		(ref. to 1971) F. Dennis ‘Old Bailey’ Homeless in my Heart 179: Beginning to learn what is meant [...] By ‘bird’ or ‘a nice jam roll’.

3. the anus, as in ‘arsehole’; thus a pej. description.

2003

B. Dark Dirty Cockney Rhy. Sl. 69: Any one with any sense knows that all jazz musicians are jam rolls.