If you are using Character pawn, then the pawn’s desired transform is already being sent to the server regularly
In that scenario you might only need to Set Control Rotation on the controller. I don’t remember whether the CharacterMovementComponent sends that to the server or not, though. You’ll have to try it and see. If this is the case and you’re using Character pawn or child class of it, then you could simply Set Control Rotation on client side to face the cursor and it should replicate to everyone correctly. Sorry I’m not at my unreal computer right now to check on this myself.