Roscoe has previously worked for
His Majesty's Diplomatic Service in
Iraq,
Sierra Leone and the
UK Mission to the UN. Between 2006 and 2009, Roscoe was the chief press officer to prime ministers
Tony Blair and
Gordon Brown. In 2017, he joined the Department for Exiting the European union as Communication Director and from 2019 to 2022 was the United Kingdom’s Ambassador to the General Assembly of the United Nations in New York. In September 2025, Roscoe became chargé d'affaires ad interim to the United States for the second time following the dismissal of
Peter Mandelson as ambassador by prime minister
Keir Starmer, amid controversy surrounding Mandelson's association with the convicted sex offenders
Jeffrey Epstein and
Ghislaine Maxwell. He previously served in that position in February 2025, between the departure of
Karen Pierce and the appointment of Mandelson. ==Early and personal life==