How do we get him without losing any roster players?
Depends how you define "any." But if you want to keep the primary rotation (including Amir but not Jerebko or Zeller) you convince the Pacers to take only the 2017 Nets pick, resign Amir for no more than $10 million, release/renounce Jerebko/Zeller, officially complete the George trade using cap room, then re-sign Olynyk. This would let you add George to the current rotation without losing any regulars.
The downside is that the following summer you have IT, Bradley, Smart, and George (and maybe Amir if you only signed him to another short deal) all hitting free agency at the same time, so you only get such a roster for a single season.