Green’s Dictionary of Slang

(US drugs) a term meaning ‘the drugs are on their way’.

1936		D. Maurer ‘Argot of the Und. Narcotic Addict’ Pt 1 in AS XI:2 125/2: rizolin. Peddler-addict argot meaning, perhaps, ‘the stuff is rolling,’ i.e., ‘your order is filled.’.
1959		J.E. Schmidt Narcotics Lingo and Lore.