WASHINGTON — Chief Justice John Roberts said there is more the Supreme Court can do to “adhere to the highest standards” of ethical conduct, an acknowledgment that recent reporting about the justices’ ethical missteps is having an effect on public perception of the court.Speaking at a law dinner Tuesday where he was honored with an award, Roberts provided no specifics but said the justices “are continuing to look at the things we can do to give practical effect to that commitment.”He …