“Rollboy” is the sonic manifestation of a London snowstorm. It’s the musical version of a dodgy geezer in a tracksuit giving you the stink eye while you cross the street to go buy a little something from an unnamed source. It’s a whole lot of paranoia crammed into a single track. This is UK garage, of a sort, skippy and menacing with a technoid edge. Both the British producer Commodo and the Turkish producer Gantz are respected, low-key entities in the world of proper underground bass music; the frosty-as-hell “Rollboy” is a display of their combined powers in action.