I roll out in the open. I used to hige my rolls, so I could fudge them if necessary, but then I'd get angry when I'd throw a really tough encounter at the PCs, and they'd make it through no problem (which would happen often, since I'd fudge so much). Then I played with some DMs who always rolled right in the open, and let the dice fall as they may, and it was so... liberating. Sure, a player would take a critical to the face when they were weak every now and then, but if you don't want bad things to happen sometimes, why play a game with dice?
And, having been on the other end, I can say I very much prefer when the DM rolls out in the open. I had a DM who would fudge every other roll (even when he was a player, which frustrated me to no end), and it really killed the suspense. He would purposely throw powerful enemies at us (a 3.5 Balor when we were level 10? Sure!) and then basically hand the battle to us (in the case of the Balor, he purposely killed off a player, only to bring that player back to life the next round, and then gave that player an automatic one-hit-kill crit on the Balor, and then- what's that? Death throes? Oh, said player somehow shielded everybody). It would have been fine if he would explain certain fudged encounters (like the aforementioned Balor incident) as scripted parts of the story, but he did stuff like this all the time (often on the fly), and he still gave out full XP for them.
As far as DM screens are concerned, I like the idea of them, but in practice, I hate them- it makes it hard to manipulate minis and such without constantly standing up and sitting down, and it puts a wall (literally and figuratively) between the players and the DM, which I don't like. I'd love to have all sorts of charts and maps and whatnot easily within my view, but in my experience, DM screens aren't the way to go.