In 1997 Rosimannus and Kristen Michal (later secretary-general of Reform party) established a club for young politicians which now has 4000 members.

She managed the district for 2 years, during which she initiated a thematic plan for high-rise buildings, a comprehensive plan aimed at the protection of the built-up area of cultural and environmental value, discussions on the future of the Old Town; she also managed to tidy up Musumägi, arranged the lighting of Schnell Park and Lembitu Park, helped modernize several kindergartens in Tallinn and summoned the round tables of the headmasters of schools, heads of kindergartens as well as apartment associations.

After the breakup of the Tallinn city coalition in 2005, Pentus-Rosimannus became the head of Prime Minister Andrus Ansip's office.

Pentus-Rosimannus is also a member of parliamentary groups of Great Britain, USA, China, Ukraine, Azerbaijan, Slovakia, Germany and Turkey.

On 1 July 2015, Pentus-Rosimannus resigned following the Tallinn Circuit Court decision which made her partly liable for debts accumulated by her father's bankrupt company Autorollo.