DM doesn't roll for them.
DM just uses the flat passive perception scores they have that don't come from rolls.
Passives aren't supposed to be rolled, the score is just high enough to beat DC or it's not. Rolling is only for actively done things.
Yes, that is absolutely how 5e rules work. However, as I indicated upthread sometimes I will make secret rolls for my players when I know their passive score isn't high enough to locate something, but a character has proven over the course of the campaign to be wary of danger or on the lookout for hidden secrets. Sometimes a player is distracted by other things and doesn't ask to search for danger, even though I believe their character would. In those cases, I'll frequently make a "secret" roll behind the screen. A lot of times if my players notice me rolling something and not saying anything, they'll immediately indicate that they'd like to actively search anyway.
None of that changes the fact that the OP and those who agree with him, SHOULD have a method for not having to see Metagame knowledge if it affects their immersion. There is currently a mod for just that thing. Hopefully at some point in the near future it just becomes something you can adjust in the options, much like Karmic Dice.
