After Marine Corps retirement the Rothwells moved to Massachusetts where they resided for the next seventeen years; first in Georgetown, and then in Andover. During ,this period Col. Rothwell worked in the Aerospace Industry in the Program Office, AVCO R&D, Wilmington, on the Minuteman II Project (Re-entry Vehicle) and ,then with Raytheon Company in the Bedford Program Office for the PATRIOT Missile Intercept System. Upon Col Rothwell's retirement in 1977 from Raytheon, the Rothwells relocated to San Diego, Mrs. Rothwell's home town.

Col. Rothwell's wife of 60 years, Phyllis, the mother of their two children, sons Richard and Charles, died in 1998. In 2003 Col. Rothwell married Rebecca Guthrie Hopkins, an Army widow of 57 years marriage. The Rothwells and Hopkins were long time friends having met on a tour to Russia in 1979. They reside in Catonsville, MD in the Charlestown Retirement Community.