These chords all belong to melodic c-minor:
B♭ is the VII (♭) of Cm melodic downward (identical with natural minor and the aeolian scale). The VII isn’t augmented.
C, B♭, A♭, G ... is the upper tetrachord downwards. G/B is the 1st inversion of the dominant chord containing the leading tone B.
The Roman numbers are:
i - V6 - VII - iv6 - VI - III64 - vii dim
The melodic minor scale has a “flat” seventh (vii natural) ... relative to E♭ major! and a sharp seventh “borrowed” from the major dominant G in respect to the leading tone B.