Since Alito, Thomas, and Scalia dissented, we can assume that the majority opinion was more about the striking down than about the stopping the injunction. Did Roberts go along with the overturning of provisions to get the one smack to the 9th Circuit, or did he really agree with the three libs? Of course you can't ever be sure about Kennedy. But if Scalia, Thomas, and Alito were on one side, you can be sure that, from our POV, that was the right side to be on.
But if it had been 4-4 (Kagan recused), would that have meant no possible return to the SCOTUS when a full Court could rule? Thus ruling now was the only way to lift the 9th's stay? That's the only reason I can at least hope that Roberts went along with strking down three provisions--because if his judicial philosophy really did lead him to agree with striking down those three parts, then we're much more screwed than we ever knew. Could Roberts be the new Souter?