To shed any payroll they have to move Robertson or Oettinger. Johnston i suppose could be an option, but most teams keep young centers more than wingers. Seguin, Hintz, Heiskanen, and Seguin have full NMC's so they're all likely out on a trade.
Rantanens already among the highest paid wingers in the league. I don't think it makes sense to then extend robertson and then have the two most expensive wingers in the league.
Working JJP under is challenging, probably requires Dumba be included, and maybe a 3rd team for Lyubushkin. It's why it might make more sense for it to be Tuch - with rosen/Östlund, probably this years 1st, and probably next years 1st (maybe you can throw a lottery top 3 protection on it).
Nuclear option would be they move both Robertson and Oettinger - and then definitely need a 3rd team to accommodate some of the other pieces that would need to be included while getting dallas NHL ready prospects, cheaper contracted players, and a goalie. Like Dallas doesn't need Byram, but what buffalo gets for byram, plus the above trade, plus levi... etc. Buffalo would need to shed UPL somewhere too. The amount of moving parts would be insane. The stuff madden dreams are made of 🙂