Rosanna served as the first Sri Lankan Female Asia Representative (2001-2003) and then Co-Secretary General of the International Lesbian, Gay, Bisexual, Transgender and Intersex Association (ILGA) (2003-2008).

Through her guidance, in 2015 EQUAL GROUND commenced Diversity Equity and Inclusion programs within the corporate sector and to date has sensitised over 45000 staff members of over 50 companies in Sri Lanka.

[2] In an interview with The Huffington Post, Flamer-Caldera said that after coming out she moved from Sri Lanka to San Francisco at the age of 18, and in 1978, she attended her first gay pride parade as a spectator, which was led by Harvey Milk.

[4][2] As well as working for LGBTQI rights, she is also an environmental activist, running a kid's environment club and other events for protection of wildlife and jungles (1990 - 1998).

In addition she has contributed as an NGO Advisor for Berlin based Hirschfeld Eddy Foundation[7] and the Global Fund for Women.

[9] She was also voted the Toronto Pride’s International Grand Marshal for 2007 for her contribution to the promotion of global human rights.