 In the 15 years after RFR Holding was established in 1991, Rosen acquired a large portfolio of office buildings, including the Seagram Building, purchased for $375 million from the Teachers Insurance and Annuity Association in 2000, and Lever House.In 2006, Rosen partnered with Ian Schrager, a longtime friend and co-founder of Studio 54, to transform the 123-year-old Gramercy Park Hotel by using minimalist architect John Pawson.In 2014, they put the hotel on the market for $260 million, after completing a 4-year $200 million renovation.