Green’s Dictionary of Slang

1. (US black) a woman of 28-40 years old [play on SE roaster, a (large) chicken / chicken n. (1)].

1941

D. Burley N.Y. Amsterdam Star-News 8 Mar. 13: When you hear the boys talking about ‘fine fryers, mellow broilers, fine young hens, roasters, and stewers’ they’re [...] describing the womenfolk [...] a roaster is 38 to 40.

2. (Scot.) a heroin user [? the heating of heroin; roasted adj.].

2013

T. Black Ringer [ebook] I turn and head back to the bedsit and the two tripped-out roasters in Adidas. They're sniffling and shivering and I know already what it is they're after.