Funny you should ask this question. Some reddit guy went through the playoffs last year and apparently everyone got torched by LBJ except Jae Crowder, which is to be expected. (Here's the link:
https://www.reddit.com/r/bostonceltics/comments/8iqoxz/how_lebron_james_destroyed_the_celtics_in_2017/).
Brad is going to start out by switching. If he doesn't switch, he's really got to trap the PnR, and then, as they say, if LBJ can beat the trap, it's 4-3 the rest of the play and giving up open 3s is a fast way to lose the game.
I think the Cavs are going to try out a variety of different switches but when they need a bucket, they will get Rozier switched onto LBJ. It will be interesting to see how BOS defends that.