Member of Europe Ecology – The Greens (EELV), she has been widely seen as a figurehead of France's MeToo movement against sexual violence, and describes herself as an ecofeminist.

[4] In 2016, Rousseau was one of several female politicians – including Isabelle Attard, Elen Debost and Annie Lahmer – who made headlines for accusing Green party colleague and MP Denis Baupin of sexual harassment.

[7][8] In March 2020, Rousseau was elected president of the Conférence permanente des chargés(e)s de mission égalité et diversité (CPED), which is composed of ninety-four public institutions of higher education and research around equality and diversity policies.

[9] In 2021, Rousseau was a candidate for the open primary vote organized by Europe Ecology – The Greens for the 2022 French presidential election.

[19][20] On 12 November 2023, she took part in the March for the Republic and Against Antisemitism in Paris in response to the rise of anti-Semitism in France since the start of the Israel–Hamas war.