She was born in a wealthy family, educated in a girls school and took part in charity as an adult. One of her friends, Hulda Hahr, was a teacher at a girls' school in Limestone, a town near Charleston in South Carolina in the United States, and offered her a position on the school. She traveled to the United States in 1851, and stayed there for four years. Roos was first a teacher of French at the school in Limestone, then she became a governess at the plantation of two of her students, Eliza and Annie Peronneau. She later wrote a description of her stay and of the culture of the American South. She did not notice any abuse of the slaves herself, but she considered slavery to be unnatural and "emotionally disgusting," and was convinced that its abolition was unavoidable, though it would meet with much resistance. She returned to Sweden in 1855.

In 1859, she founded the paper "Tidskrift för hemmet" (English:"A Paper for the Home") in companionship with her friend Sophie Adlersparre with financial support of Fredrika Limnell. The paper was a feminist publication, which argued for women's rights, particularly the right to higher education and profession. They wrote many of the articles themselves. In 1861, Roos and Adlersparre made a journey through Germany, France, England, Scotland and Ireland to compare the difference within the feminist movements, and reported that the movement was little known in Germany and France in comparison to Great Britain.

In 1864, she took part in the founding of the Swedish Red Cross (1865) with Adlersparre, General Major Rudebeck, and Dr. Lemchen.

In 1857, she married the statesman Knut Olivecrona.