I have read a bit on the subject-the Rosenberg’s involvement (both of them-husband and wife) were verified as Soviet spies when a lot of Soviet-era intelligence was released.
The Venona Files (Soviet communications that we were able to read because we had broken their code) provided indisputable proof that both the Rosenbergs were involved.
Because we were able to decrypt their communications we were able to see what the Soviets were saying, but were mostly unable to positively confirm exactly what they were discussing until the fall of the Soviet Union enabled us to see their documentation and cross match to various elements.
The worldwide outrage against the Rosenbergs was orchestrated by the Soviets and the worldwide Communist party.
Morton Sobell, who was the last convicted person in that case who died in 2008 admitted he was spying for the Soviets (and said that Julius Rosenberg was as well) in an interview before he died. He did say Ethel Rosenberg was not part of the ring, but I don’t believe him. He spent his entire life lying about it.
The Rosenbergs were both committed communists and admitted that openly, saying they were being prosecuted
After reading extensively about the CPUSA and such (from a variety of different sources) the concept that his wife wasn’t involved given her commitment is unsupportable. That wasn’t the way those people operated.
The Rosenbergs were true believers. They devoted their entire lives to their faith. They spied for their faith. They lied for their faith. They died for their faith. I have never questioned their courage or their integrity. They were communist heroes. I.e., heroes on the wrong side, morally no different than the devoted SS men who died in the rubble of Berlin because their Fuehrer had ordered it.