Oh, dear...I'm afraid you have been given the wrong information. I just googled both Roosevelt and Eisenhower and I did find websites that stated the both of them (plus Stalin!) had Jewish ancestry, but those sites were right-wing or anti-semitic sites. Here's the straight answers:
Roosevelt's main family tree derives from the Netherlands, although Franklin, on his mother's side, had ancestors on the Mayflower who were English. During World War 2 the Nazi propaganda machine put out a claim that Roosevelt's family name was originally Rosenberg, a Jewish name, and the family changed it to cover this up. Sheer Nazi nonsense.
Dwight Eisenhower had no Jewish ancestry.
Both of his parents, David and Ida Stover Eisenhower, were from families of German immigrants who had Protestant religious affiliations. The rumor that Dwight Eisenhower had some Jewish background was started during the 1952 presidential campaign by certain far-right fringe groups
who opposed his candidacy. The West Point year book, The Howitzer, for 1915 contained a "tongue-in-cheek" description of Ike which began as follows: "This is Senor Dwight David Eisenhower, gentlemen, the terrible Swedish-Jew, as big as life and twice as natural. He claims to have the best authority for the statement that he is the handsomest man in the Corps and is ready to back up his claim at any time." Right-wing
groups reproduced this page from the Howitzer and used it to accuse Eisenhower as being part of a Jewish conspiracy. Eisenhower, of course, was neither Swedish or Jewish. Some historians have suggested this may have been a reference to Ike's having blond hair and being tight with
his money. "