I was intending both by Dmap, but I'm also using the same message script to play a message on the first room (which was intended to do the same).
Basically, I'm using one string as a Dmap Intro string (which would be convenient to do once per Dmap no matter where you enter, in case of multiple entrances - so you can't enter one way, then see the message when you try to exit by the other way), and another one in the boss room, for the boss to talk to you (this is also why I want to have the enemies disappear when you defeat them). The issue is that in some of my dungeons you can go back into these boss rooms before you leave, meaning awkward repetition of lines and a revived boss.
If there's no way to work around this (I do have a dungeon with two bosses), I can work around the ability to return to the boss rooms (meaning I won't need my second request).