After the war, John Aspinwall Roosevelt pursued a business career in California as the Regional Merchandising Manager for Grayson & Robertson Stores in Los Angeles. In 1953, he became a partner in a Beverly Hills financial company but left shortly thereafter to take up residence in the family compound in Hyde Park. Unlike his siblings, Roosevelt intended to “work his way up” without seeking to profit from his name and connections. However, his department store work was under the wing and direction of Walter Kirschner, a Roosevelt family friend who mentored and subsidized many of the siblings in the 1940s. He was also involved with Elliott Roosevelt in several businesses, especially in Cuba after Fulgencio Batista took power in 1952. Roosevelt represented François “Papa Doc” Duvalier in the United States and attended his inauguration. By 1958, it was reported that Haiti “has retained the P.R. firm of Roosevelt, Summers and Hamilton at a fee of $150,000 to act as its public relations consultant for one year.” Although he never pursued political office, Roosevelt served on the boards of many organizations, including the Greater New York Council of Boy Scouts of America, the Eisenhower Exchange Fellowship, Roosevelt University, the State University of New York, and the Governmental Affairs Committee.

Although John Aspinwall Roosevelt leaned Republican at an early age, he deliberately kept an apolitical stance until after his father’s death. In 1947, John Roosevelt changed his political affiliation to Republican, a gesture his mother interpreted as an attempt to win support from his wife’s family, his father-in-law being a staunchly Republican Boston banker. But in 1952, he went beyond paper registration, actively supporting Dwight D. Eisenhower’s bid for the Presidency against Democratic nominee Adlai Stevenson, for whom his mother was just as actively campaigning. His defection from the Democratic Party and his subsequent leadership of Citizens for Eisenhower – he vocally defended Eisenhower’s running mate, California Senator Richard Nixon, against attacks by his mother – caused considerable family friction. The tension was exacerbated when Roosevelt and his family moved into Stone Cottage next door to Eleanor Roosevelt’s home at Val-Kill that same year. He and his brother, Elliott, who lived at nearby Top Cottage, did not get along. Elliott left shortly after John and his family arrived. John subsequently acquired what remained of the Hyde Park property Elliott had farmed with Eleanor Roosevelt. More importantly, the presence of John and his family enabled Eleanor Roosevelt to live at Val-Kill until her death in 1962. She saw John’s children often and was particularly close to his daughter, Sara “Sally” Roosevelt. After Eleanor Roosevelt’s death, John kept the papers from her Hyde Park home and New York City apartment. Within three years of Eleanor Roosevelts’s death, John Roosevelt divorced and remarried. In 1970, he sold the Val-Kill properties. Thereafter, he and his second wife lived on an estate in Tuxedo, New York. John Aspinwall Roosevelt died of heart failure in 1981.