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Just have some of the other PCs who are obviously the rogues friend try to convince him to go into the room. The demon is not there to argue against this and its Charm Monster not Dominate. Once another PC makes a good arguement and make a charisma roll I would say the rogue has no reason not to enter the room.
I don't claim to be an expert. I assumed since there was a Charm Person that only affected humanoids, that Charm Monster would NOT affect humanoids. If that's not the case, my mistake. I'm also not in a positive frame of mind.