Robbers was the FMA's director of strategy, risk and assurance and has also been at the Securities Commission.
Hawkesby is leaving Harbour Asset Management, which he helped to set up, to become assistant governor and general manager of economics, financial markets and banking on March 18.
He will be responsible for monetary policy formulation and research; monetary policy implementation and liquidity management, and foreign reserves management; and all matters relating to currency creation and distribution, including responsibility for the management of the payment and settlement system.
"Bringing these activities together provides end-to-end management of all of the monetary policy activities ... from currency creation and distribution through to the setting of the official cash rate."
Hawkesby was also at the Bank of England for nine years.
The new structure saw the departure of Sean Mills, head of operations, Mark Perry, head of financial markets, and Klarissa Plimmer, chief information officer.
John McDermott accepted a role as chief economist and a department head, but has since left to join the economic research institute Motu as an executive director.
Bernard Hodgetts, head of macro-financial, was to leave when his secondment to Treasury for its Reserve Bank review ended.