If he wanted to honor them, why didn't he keep their last name?
"If he wanted to honor them, why didn't he keep their last name?"
He and his brother Michael were adopted by some lefty songwriters:
"The Rosenbergs' children
The Rosenbergs' two sons, Robert and Michael, were orphaned by the execution, and no relatives dared adopt them for fear of ostracism or worse. They were finally adopted by the songwriters Ann and Abel Meeropol. Abel Meeropol wrote the classic anti-lynching anthem "Strange Fruit," made famous by singer Billie Holiday. Robert and Michael co-wrote a book about the experience, We are your sons: The legacy of Ethel and Julius Rosenberg (1975), and Robert wrote another book in 2004, An execution in the family: One son's journey. In 1990, Robert founded the Rosenberg Fund for Children, a non-profit foundation which provides support for children whose parents are Left-wing activists involved in court cases.
Michael's daughter, Ivy Meeropol, directed a 2004 documentary about her grandparents, Heir to an Execution, which was featured at the Sundance Film Festival."
http://en.wikipedia.org/wiki/Rosenbergs#The_Rosenbergs.27_children
All of the descendents have managed to make nice careers out of being the offspring of the Rosenbergs.