As other reviewers have mentioned, this is essentially an amateur effort, but I believe it is more effective for that, and that a more polished, careful effort by "professionals" would not be nearly as poignant and effective.
Though many of the Rosenberg family cling to various pieces of the puzzle hoping, or pretending, that Julius & Ethel were either "innocent" or at least deserved a lesser punishment, it is clear from the Venona transcripts (released in '95) and testimony of ex-KGB agents that they were active -- Julius much more so -- in stealing highly classified U.S. secrets and giving them to the Soviet Union, as part of an organized socialist-communist cabal. They were clearly "true believers," which is what essentially scarred their children's lives.
As this film makes quite clear, the Rosenbergs could have spared themselves right up to the day they were executed, but their refusal to implicate other spies sealed their fate. However misguided, they were true believers, willing to die rather than betray their cause.
At this late date there is of course not the slightest doubt that both were guilty of treason and espionage, and, due to their refusal to "betray" their comrades or their cause, they also inflicted great emotional trauma to their families, especially their children. One cannot help but sympathize with them, but it's hard to argue that their parents are in any way "innocent" or did not commit treason and espionage. They opted to die. One can only bemoan the fact that others in the ring deserved death far more than Ethel, but got light sentences.
Though a bit long and slow-moving at times, for someone interested in this peculiar historical incident this film will prove fascinating despite its less-than-polished production.