My own entry, on July 22d (my site is not searchable) had this about Roberts' dissent in United States v. Jackson, 415 F.3d 88 (D.C. Cir. July 22, 2005), released just days after he was nominated:

Author's comments: So, what does this tell us about Judge Roberts? He defers to the police choice of a course of action, based on their experience. It is true that experience often forms the basis of probable cause and reasonable suspicion determinations, but we have to remember that Ornelas requires de novo review of these determinations. How sensitive will he be to the Fourth Amendment when he gets to the Supreme Court? He can talk the talk about "the Fourth Amendment’s place among our most prized freedoms," but it is too soon to tell if he can walk the walk. He seems to fall over himself to volunteer that he adheres to the values of the Fourth Amendment, and then he hands them to the police to decide whether the people should have them.

Anthony Amsterdam's famous line from 1974 about reasonableness and police discretion comes to mind: "What it means in practice is that appellate courts defer to trial courts and trial courts defer to the police. What other results should we expect? If there are no fairly clear rules telling the policeman what he may and may not do, courts are seldom going to say that what he did was unreasonable." Anthony Amsterdam, Perspectives on the Fourth Amendment, 58 Minn. L. Rev. 349, 394 (1974). Ornelas was supposed to have prevented that. In Judge Roberts' world, the police decide on reasonableness, and judges defer to that determination.

If deferring to the police is the essence of reasonableness, those who believe in a strong Fourth Amendment would say we are in trouble. Judge Roberts gives me pause by this passage, quoted above: "Finally, my colleagues’ insistence that police should have further questioned Jackson amounts to prescribing preferred investigative procedures for law enforcement. We have neither the authority nor the expertise for such an enterprise."

It almost sounds if he's catering to those who equate "activist judge" with any judge that disagrees with the government.