ElRoy was born January 29, 1921 at Summit, South Dakota and was adopted by Anton and Clara Iverson at Roslyn, South Dakota in 1926. He married Renata Schaunaman in 1942 and had two children: Dennis in 1943 and Eileen in 1945.

ElRoy served in the army during World War II in radar stationed at Camp Davis, California. After the war, he earned his Bachelors Degree in Mathematics in 1950 from Northern State Teachers College in Aberdeen, South Dakota. He taught mathematics in South Dakota from 1950 to 1954. In 1954 he completed his Masters Degree and moved to Torrance, California. He taught mathematics in Torrance, Bellflower, and San Pedro, California until his retirement in 1980.

After his retirement in 1980, ElRoy and Renata moved to Mission Viejo, California, where he continued to work as a plumber and handyman for his community in Casta Del Sol. After the death of Renata in 2000, he married Millie Jo Holliday in 2002. Millie Jo passed away in 2008.

ElRoy was a "perfectionist" in everything that he did. He was a "do-it-yourself" person who could fix anything. He was also a brilliant mathematician and excellent teacher. His hobbies and passions were dancing, bridge, and bowling. He enjoyed dancing with Renata through the years to the Lawrence Welk Orchestra at Pacific Ocean Park in Santa Monica; his favorite dance tune was "In The Mood". He played bridge with his son for 60 years and was a Gold Life Master; they reached the finals of the North American Pairs in 1982 and 1993. ElRoy was known as "The Joker" both at school where he taught and the bridge table because he always had a joke or riddle to share. His trademark was his blue stocking cap.