Rollers aren't a good basis for tire rolling resistance tests. The curvature of the roller changes the rules because the contact patch isn't flat. But that's besides the point. There's no debate (or shouldn't be) whether the same tire has lower rolling resistance at higher pressure on flat roads.

But the rate of change in rolling resistance diminishes as the pressure goes up, so the incremental improvement may be more than offset by other factors (if they apply to the actual situation).