In addition, it's late in the term. The Court traditionally leaves contentious decisions for late so most watchers assumed some of these cases would produce 5-4 outcomes. Instead the Court went 9-0 on buffer zones (no zones), 9-0 on searches of cellphones (no searches without a warrant), and 9-0 on recess appointments (no, three days does not constitute a long enough time for Congress to be considered in recess). That suggests that the Justices saw compelling positions to which they could all sign on, regardless of their ideological leanings.
I give Roberts and the other Justices thumbs-up for showing that compromise is still possible somewhere in government.