Video trickery is not magic. There's a difference between appearing to put a ball under a cup when you actually palmed it, versus actually putting the ball under the cup, turning off the camera, taking the ball out from under the cup, turning the camera back on, and then showing that there's nothing under the cup. The former is being a magician, and the latter is being a fraud.

Another: suppose I ask an audience member to think of a number, and they say "217". I say that I predicted that they would say "217", and pull a piece of paper out of my pocket that says "The audience member will say '217' ". If I used subliminal messages to prompt them to say "217", that's mentalism. If I managed to write "The audience member will say '217' " on a piece of paper and slip it into my pocket without anyone noticing, that's sleight of hand. If the audience member is actually in on it, that's just bare deceit. That's not to say that having confederates is illegitimate, but if the entirety of your trick consists of confederates, that's not magic.

In some of Derren Brown's tricks, mentalism, sleight of hand, and trickery are all credible hypotheses. But for many of them, there's simply no way he could have done it through sleight of hand. Either he did it through mentalism, or he did it through trickery.

I don't know what the details of the Russian roulette trick were, but my inclination is to doubt there was sleight-of-hand.