[shevegen]

The only real way to enforce roleplaying is to mandate of the players to play a virtual character.

Ideally only one, at least as a main character, and the others without falling into the multiplayer-trap.

You need to give players the freedom and the tools to roleplay and portray their characters in ways that are fit.

Strive for maximum consistency within the game world and have the tools encourage this.

Be story driven.