A couple of earlier - albeit now rather old - threads address this question. You might find them helpful.

Did ancient civilizations have banks? When did ideas like loans with interest come about? with u/PlinytheHipster (covers both Greece and Rome)

How did the Roman bank work? with u/yemrot

How did Roman senators/businessmen actually store and secure their wealth? How much was liquid, how much was tied up in assets? with u/qsertorius