They were proud. I'm not sure what else there is to say about it. Theodore Roosevelt wrote about his Dutch roots in his autobiography, where he recounted the roots of the family's immigration to America in the 1640s, so it had either been handed down or someone in his family had done the research and he was proud to recount it for the masses--his autobiography was first published in 1913. In the book, he wrote of his grandfather teaching him a little Dutch when he was a boy. Roosevelt was baptized in the Reformed Church (originally the North American branch of the Dutch church in America) and maintained membership in the church throughout his life, even though neither of his wives belonged to the church (his second wife was Episcopalian, I'm not sure about his first wife, but she wasn't Reformed, either). He was a member of the Holland Society of New York, a club dedicated to promoting the preservation and study of documents from the Dutch period of New York history.

Franklin Roosevelt was also proud of his Dutch roots. He grew up in the "Springwood" estate owned by his father in Hyde Park, New York, which is now a museum, and in it hangs a portrait of the immigrant progenitor of the family, Claes Martenszen van Rosenvelt, which had been handed down over hundreds of years through many generations. FDR was a genealogy enthusiast, and was also a member of the Holland Society, serving as a Trustee of the society while he was governor of the state of New York. He also belonged to the Dutchess County Historical Society--Dutchess County is the county in which he grew up and it had a significant Dutch population in colonial times.

While governor, he wrote the introduction to Dutch Houses in the Hudson Valley before 1776, written by Helen Wilkinson Reynolds and published by the Holland Society. The book contains a collection of photographs and historical descriptions of surviving Dutch buildings in upstate New York. While President, in 1936, FDR wrote the introduction to the follow-up book Pre-Revolutionary Dutch Houses and Families in Northern New Jersey and Southern New York by Rosalie Fellows Bailey. FDR gave at least one speech to the Holland Society while serving as U.S. President, and one day while "relaxing" during the presidency, he spent the day transcribing old records from Dutchess County. The book is called Records of Crum Elbow Precinct Dutchess county, New York, 1738-1761 and was first published by the Dutchess County Historical Society in 1940.