It would be a mistake, I think, to assume that Scalia and Roberts would have voted to deny rehearing if any member of the majority had voted to grant rehearing. The fact that no member of the majority voted to grant rehearing confirmed Scalia’s and Roberts’s perception that (in Scalia’s words) “there is no reason to believe that absence of a national consensus would provoke second thoughts” among the members of the majority.
In other words, I suspect that if there had been three votes for rehearing (from Thomas, Alito, and one member of the majority), Scalia and Roberts would have provided the fourth and fifth votes. If I’m right, it isn’t that Scalia and Roberts agreed with the majority that rehearing was unwarranted; it’s rather that the majority’s view that rehearing was unwarranted demonstrated to Scalia and Roberts that rehearing was futile. So no one should take Scalia’s and Roberts’s vote as somehow vindicating the majority’s decision not to rehear the case.