Roberts knew he was acting unethically
In April, Judge John Roberts heard arguments about the Bush administration’s [Guantanamo Bay] policy as he was discussing a Supreme Court appointment in private conversations with the White House. On July 15, when Judge Roberts met with President Bush for the job-clinching interview, he joined a ruling in favor of the defendants, who included Mr. Bush. The White House claims Roberts didn’t do anything wrong. Bush spokesman Steve Schmitt said “there was no conflict whatsoever.”
John Roberts knows better and we have proof (pdf).
In 1986, when John Roberts was working in the White House Counsel’s Office for President Reagan, he was asked to review a mundane request by an attorney named Lester Hyman. Roberts replied (pdf):
I must recuse myself from this matter, in light of pending discussions with Mr. Hyman’s firm about future employment.
So Roberts understands it’s unethical to make professional decisions that impact a prospective employer. When it came to the prospect of a nomination to the Supreme Court, Roberts simply set ethics aside.