She was also the leader of the opposition in Western Provincial Council and the chief organizer of United National Party for the Colombo West electorate.

Senanayake has served as the Sri Lankan High Commissioner for Malaysia[6] and was a Goodwill Ambassador for the United Nations Population Fund.

She works for the rights of women and adolescents in her country and as a United Nations Population Fund Goodwill Ambassador.

There, she served as the Leader of the Opposition until being elected to the parliament in 2010 securing the fourth place in the UNP list with 66,357 preferences.

[11] In Parliament, she has raised several prominent issues such as violence against women and children, chauvinism and socio-cultural and socio-economic problems affecting Sri Lanka.

"[13] Witnesses appearing before Presidential Commission of Inquiry[14] stated that Rosy Senanayake had leaked some secret information of the Committee on Public Enterprises (COPE) in Parliament to the Perpetual Treasuries Limited (PTL).