Drum sound
I think it could be either:
'drum sound' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for roll that I've seen before include "start a revolution" , "Furl" , "Official list of members" , "Schedule" , "Continuing success if one is on this" .)
'drum sound' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bang that I've seen before include "Sound of explosion" , "Sudden noise; fringe" , "Report - something the hairdresser did?" , "Loud noise; fringe" , "Explosion; hair fringe" .)