Roshia called the Secret Service's Boston office last month and told a receptionist, "I will kill Michelle Obama" and "I will kill Marines," according to a Secret Service affidavit.
During the same call, she said she would "blow away" Michelle Obama, the document states.
A message left at the federal public defender's office in Honolulu was not immediately returned.
Roshia has a history of leaving rambling messages and sending poems, love letters and photographs of herself to the Secret Service, according to the affidavit.
As early as 2004, she told the agency that "although her mission is to assassinate the president, she has no desire to hurt him," the document states.
The affidavit said Roshia acknowledged after her arrest that she had threatened Michelle Obama.
It also says Roshia said she knew where Obama would be staying in Hawaii, and the reason Roshia she had traveled to Hawaii in September was "to protect Obama."
Roshia was also charged with lunging at a Secret Service agent, striking him in the arms and face during her arrest.
She was being held without bail pending a Wednesday detention hearing.