 Every summer the Rosenberg family and the Picasso family would depart for the South of France, holidaying there with friends including F. Scott Fitzgerald, Somerset Maugham, Stravinsky, Ravel and Matisse.Rosenberg's reputation for clean dealing enabled him by 1935 to persuade his brother-in-law Jacques Helft, a noted antiques dealer, to open a branch in Bond Street, London, to enable them to engage with more Americans.Noted clients included museums such as the Museum of Modern Art (MoMA) (of which Rosenberg was an early supporter and donor), and the Philadelphia Museum of Art.