I don't know anything about FDR's house in Oyster Bay, but Sagamore Hill, which was the home of Theodore Roosevelt,

is definitely in Oyster Bay. I'm from Long Island and my parents took me there when I was a kid. It was really interesting. There is a website for Sagamore Hill - http://www.nps.gov/sahi - which gives directions by car or by Long Island Rail Road.

Jamie Natick, MA