Previously Romilly was CEO Infrastructure Australia (IA). Before joining Infrastructure Australia, Romilly was CEO of Green Building Council of Australia for 13 years. In acknowledgment of her contribution to Australia’s sustainable building movement, Romilly was awarded an Order of Australia in 2019. 

In her capacity as CEO of Engineers Australia, Romilly sits on the STEM Champions of Change committee. She is also currently a Member of the Australian Academy of Technology & Engineering (ATSE) Infrastructure Forum; Director Placemaking NSW Board; Member Infrastructure Net Zero Steering Committee; Chair UNSW Institute of Industrial Decarbonisation IAC; Federal Government appointee on the Circular Economy Ministerial Advisory Group, and G20 EMPOWER; Member Industry Skills Australia's IAC; Member National Women in Transport CEO Advisory Group; Independent Chair Currawong State Park Advisory Board (NSW); Member UK Institution of Civil Engineers Enabling Better Infrastructure (EBI) Steering Group and Director of Minerva Network (supporting Australia’s elite sportswomen).

Romilly is an active surf life saver on Sydney’s Northern Beaches.