The "game" Russian Roulette origins from 19th century Russia - hence the name - and was done by some dumb ass aristocrats. Preferably when they were full to the brim with Vodka. It was for one seen as a proof of courage, but also it was about profit.
The question if you can tell if a round is in the revolver or not is matterless. It was played with only one gun, and that had always one round in it. The rules are simple:

• some blue blooded idiots, who don't know what to do with their lives, sit around a table.
• a revolver, preferably a Nagant, is loaded with one round. Then the cylinder is spun, so nobody knows where the round is.
• then the first idiot puts the gun to his head and pulls the trigger. If he has bad luck, a new round is loaded into the gun.
• In any case, the gun is passed on to the next idiot. He also pulls the trigger on his head.
• This is continued until only one idiot is left, or several remaining idiots agree to call it a day.
• The survivor/survivors get all the posessions of the dead. Not just what is in their pockets, but everything, all their wealth, real estate and so on.

As you see, it doesn't matter if you can feel the weight difference, you know there is a round in the gun anyway.