In 1904, he was transferred to Manchester United for £600. The United manager at the time was Ernest Mangnall who had embarked on a spending spree which would later see Manchester City players Billy Meredith and Sandy Turnbull arrive at Bank Street, United's ground at the time. Roberts arrival at United was extremely important to the development of the club; a strong, skilful, fast centre half and a rebel to boot. He flouted FA rules by wearing his shorts above the knee and was politically minded in favour of the unionisation of professional footballers.