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Frank Rosenau, 95, of Lemmon, SD, passed away on Friday, February 13, 2026.

Visitation for Frank will be held at 6pm on Friday, February 20th at his ranch- 11162 Hwy 73, Lemmon, SD, followed by a family service at 7pm. Frank's funeral service will begin at 10am on Saturday, February 21st at the ranch, followed by burial at Greenhill Cemetery.

Franklin Otto Rosenau was born on October 26, 1930 in Dupree, SD to Otto and Ruth Rosenau.  He joined 3 sisters, Helen, Clara, and Adeline and was later blessed with brothers Darrell and Fred. The family resided in a small homestead near Thunder Butte until 1936 when they moved to Raymond, SD.
In 1945 Frank left high school. He spent time doing odd jobs.  When Frank was about 18, he began employment on the flood control projects of the Missouri River.  He was hired as a mechanics helper and soon moved to test driving the machines.  Many times, instead of taking lunch breaks, he would ride along with an operator and learn about the machine.  They would, at times, allow him to drive.  He gained much knowledge and experience through this endeavor.   Through this knowledge and experience, he was able to gain employment working on the Garrison Dam, the Fort Randall Dam, and lastly the Oahe Dam at Ft. Pierre.  He loved the challenge and the time of learning about the big machines.
On July 29,1957, Frank married Arleen Miles at Gettysburg, SD.  In 1964, they bought the grocery store in Lebanon, SD.  The store was successful and Arleen did well holding the fort as Frank stayed busy with grocery and milk deliveries.  Frank then purchased a semi and trailer and started hauling corn out west at night.  He also completed deliveries and any repairs that may need to be done during the day.  He even managed to blow the store up when he was trying to fix the freezer.
On January 23, 1969 the first of 5 children were born to this union.  They were blessed with the family they had dreamed of Joel, Adeline, Joyce, Jennifer, and Kay Lynn.  Seeing they would need more room, in 1970 Frank bought the US Air Force radar base north of Gettysburg SD.   The family resided there until moving to Lemmon in 1988.  Here Frank and Joel continued doing dirt work.  The new home was near the lake.  Frank held a love of waterskiing; therefore, it was the perfect location for entertaining friends and family.  Frank loved to have people around and a good meal made it even better.
Even in his last years, Frank had successfully water skied at age 90 ….and had hoped to do so again!!  Frank continued working in any way he could.  Although, in the last days just moving from the chair to his scooter had gotten to be work, he was still planning to go dig in the dirt come spring.
After Arleen passed in 1999, Frank remarried. His last wife JoAnn passed in 2023.
Thankful for sharing his life are his daughters Adeline Bird, Joyce (Todd) Peterson, Jennifer Rosenau, and Kay Lynn (Trent) Sonsalla. Stepchildren Steve, Tim, Jill, and Joye and their families. Grandchildren Denver, Joshua, Genesis Rosenau. Moriah, Jessica, Catherine, and James Bird.  Lacy, Augustus, Katie, and April Peterson.  Kiyoko, Hana, and Hiroshi Picklesimer.  Troy, Emily, Jimal and Rosie Storm. Brothers, Darrell and Fred Rosenau. Along with 21great grandchildren.
Those that preceded him in death are his parents his sisters Helen, Clara, and Adeline. His wife, Arleen and his wife JoAnn. His son Joel and his grandson Guy Peterson.