I know there are a lot of bloggers and blog readers who favor rolling all the dice in the open. The original West Marches campaign, which I'm not faithful to 100%, also was for open rolls by the DM.
Now, I've come to believe that in combat, yes, the rolls should be open. Fair combat rolls, observed by everyone, lead to fewer complaints when things go pear-shaped.
But sometimes, rolling in secret as a DM for non-combat tasks is a good thing.
Searching for secret doors is a trade-off. There's not guaranteed to be a secret door where you're searching. And even if there is, you're not guaranteed to find it due to the roll. And each search takes a Turn, so the more searching done, the more chances of wandering monster encounters that suck up resources. In this case, if the roll is in the open and a result proves that there is no secret door (1-2 on a d6 for an Elf, 1 on d6 for anyone else, with no door found), the party knows to stop expending resources. But if the result is a mystery, they don't know if there is no door, or if the dice just weren't on their side (and chances are they weren't).
And now, they have to make a choice. Risk a wandering monster check to roll again? Or move on and potentially miss some treasure or a shortcut through the dungeon.
Now, I can understand the rationalization in the above situation that a successful roll where there is no door means the party gets definitive evidence that there is no door. So rolling in the open isn't so bad for that. But the suspense and measuring of odds of keeping that roll secret is more interesting to me.
Similarly, Thief skills are rolls that I, having learned from Mentzer's rules where he advises such, think the DM should roll in secret. Again, it adds to the suspense at the game table. And it's a situation where, as DM, if you were going to fudge the roll anyway, you might as well just tell the player straight up that conditions are such that they succeed automatically.
I mean, no one complains when a DM tells the Thief player, "Sorry, there just aren't any shadows to hide in here." Or if a door is barred rather than locked, so it can't be picked (although a clever Thief can work around a barred door too...). If the situation is such that failure is guaranteed, I don't see many players complaining. So if success is guaranteed, the DM should just tell the player that without bothering to make a roll.
Just like players, the DM shouldn't have to roll unless the outcome is uncertain. And while certain rolls like monsters' attacks, damage, and saving throws most definitely should be rolled in the open, occasionally there are still times when it is better for the game experience for the DM to keep the roll secret from the players.
IMO, YMMV, all that jazz.
38 minutes ago