I asked my Bulls friend this (if the pick lands #1, what else would you take back for Butler) and he said if the Nets Pick turns out to be #1, he would be fine taking the Nets Pick, Rozier, the 2019 Grizzlies OR Clippers Pick, Zeller/Amir (salary filler), and Yabusele.
He doesn't think the Bulls will deal Butler at the deadline though, so it has to be this summer, and he thinks the Bulls will want one of Bradley/Crowder still.
I truthfully don't think a Butler deal gets done. The Bulls are also winning games now and their FO is becoming as dysfunctional as the Kings one... (signing Rondo + Wade this off season made no sense especially after trading Rose..)