I'm not part of the "let the dice fall where they may" crowd. I have not seen roleplaying games as physics simulators for quite a long time. I'm actually one of those GMs who always rolled behind the screen, explicitly so I could fudge rolls in the best interest of the "story" or to make sure things went the way I wanted them to. Sure, most of the time it was to the players' benefit but there were times when the monster missed and I flipped it to a hit, or when a random encounter didn't yield an interesting result so I made it interesting. My players always trusted me, and thought I was a good GM.
But I always felt like a sham, knowing that so many times I kicked down rolling all 10s on damage dice to 5s, or I bumped the enemy's hit to a critical because the PCs were defeating it too easily. So gradually, and without quantifying the technique, I started moving toward rolling everything out in the open. If the dice were rolled, everyone around the table would be bound by those rolls. Dice were used to resolve uncertainty, when no one wanted to (or felt they could) take responsibility for the results.
|Fudging rolls makes me feel something like this|
Knowing when to roll is a skill that I'm constantly working on improving. It's what I actually want the players to trust me for. I want them to trust that I know when it's the best time to let the dice decide, when it's the best time to make a declaration sans randomizer, and when it's the best time to get a consensus. Just trusting that I'm an impartial die roller isn't enough.