Identifying signatures and attributions can be real bugaboos when reading older handwriting. However, context does matter.
In the Roosevelt documents I sometimes see signature transcriptions rendered as "Ms. XYZ," sometimes even on official State documents. Interestingly enough, while the term "Ms." was first coined in 1901, it was not in wide-scale use in any way until the 1960's, and The New York Times did not adopt it into their journalistic practices until 1986. So, it would not be used on correspondence from 1902-1912.
Likewise -- and rather sadly -- except for an occasional stenographer there were almost no government employees in the first decade of the 20th century who were women, and no Senators or Congresswomen at that time. So official State documents would almost certainly not sport a signature of "Mrs. XYZ."