She studied Spanish and French at Trinity College Dublin (TCD), attaining an MA in Modern Languages.
There she proposed the motion "That This House Reveres the Memory of Miss Pankhurst" at a debate chaired by Sheelagh Murnaghan.
[2] The society subsequently named an annual competition in her honour, the "Rosaleen Mills Maidens Final".
From 1936 to 1937 she nursed her mother full-time, after which she took a position at the commercial office of the Canadian Embassy to Ireland from 1938 to 1945.
She was involved in campaigns for women to be permitted to join the police force and also against the 1927 Juries Act which prohibited female jurors.
She took part in the IHA campaigns and was a regular contributor to The Irish Housewife, the organisation's journal.
They also discovered a number of issues relating to inequality in pay, access to education and discrimination against married women.
For most of her adult life, she lived at 37 Percy Place, Dublin 4 before moving to St Mary's Nursing Home, Pembroke Road.