For starters I don't think it's a priority to trade Rozier. We have a team assembled that can win it all. Rozier provides luxury depth, insurance for injuries and an escape if Irving decides to leave (which I really don't think so).
However, the demand for Rozier may never be higher than it is right now, since his role will diminish now that everybody is injury-free. A team that's looking for a good PG is Orlando. Morris is another guy who's minutes will be eaten and might get disgruntled. But maybe Orlando has more interest in a prospect like Yabusele? I'd be willing to throw in a pick to get Jonathan Isaac. He's got a lot of potential. Trading Morris and Rozier would get the Celtics out of the luxury tax.
Proposal:
To Boston: Jonathan Isaac
To Orlando: Terry Rozier, Marcus Morris or Guerschon Yabusele, '19 Celtics 1st or '19 Clippers 1st (prot.)