Theodora was born to Raymond and Doris Horn, on Feb 27, 1937 in Omaha, NE. She graduated from St. Cecilia's High School, Omaha and from St. Joseph's School of Nursing, Omaha, NE in 1957. She attended Creighton University, Omaha, NE and Mount Marty College, Yankton, SD.

Following nursing school, Theodora went to in Bogota, Colombia as a lay missionary with the Young Christian Workers. She married Michael A. Rossiter on August 4, 1962. Mike and Teddy moved to Yankton, SD in 1963. Theodora raised six children. Later in life, she returned to nursing. She worked at Nancy Home for the Aged and the South Dakota Human Services Center. She was a true blue member of ACLU and the Democratic Party. She was a delegate to the '68 Democratic National Convention. She was a dedicated Roman Catholic. She loved genealogy, sewing and quilting.

Theodora is survived by her husband, Michael, her six children: Cecilia Rossiter of Lincoln, NE, Lawrence D. Rossiter of Bloomington, MN, Peter Rossiter of Yankton, SD, Rachel Trabelsi of Dunwoody, GA, John (Iris) Rossiter of Burke, VA and Martha Rossiter of Sioux Falls, SD, and her three grandchildren: Ellie Trabelsi, Alexandra and Katherine Rossiter and her four siblings: Ramona (Homer) Hayes of Urbana, IL, Raymond (Alberta) Horn of Anacortes, WA, Roberta Roach of Omaha, NE and Stephen (Jane) Horn of Blair, NE.

She was preceded in death by her parents.