I'm wondering if the roll and move mechanic has any real effect on how Talisman, or any similar game, plays out. Would the overall experience be fundamentally changed if, for instance, you could only move one space at a time? I'm just trying to understand how it enhances the game relative to the other mechanics.
Roll and move is obviously there to create randomness. Talisman is all about randomness, you never know where you're going to go or what you're going to draw. Having more control over that introduces a lot of balance issues, because there are spaces that are not meant to be visited over and over again. Of course, there are a number of Talisman cards that do give you more control over where you are moving, but they are all "temporary" in the sense that they can be stolen, destroyed, etc.
The biggest issue I would see with one move at a time in Talisman is the impact on PvP. Some classes are designed for fighting other characters, while others are designed to avoid such fights. With one move at a time, there would not be a way to escape other characters, so you'd need to introduce other ways for characters to get away from someone else. Even with that, there would still be the potential to "grief" people by "camping" at a location that you know they need to get to.
As bwarner said, roll and move is meant to create some uncertainty and randomness. In addition, in Talisman (and some other games, like Titan) the player can choose the direction of movement after seeing the roll, giving him the chance to aim for some spaces and avoid others. With "always move one space" a player will either have to pass through every space on the way to his goal or thrash between two spaces. That doesn't feel like much fun to me.
In addition, Talisman does have a "move one space" mechanism: when you get turned into a toad. So if that's ever happened to your character you should have some sense of how that mechanic works out. (Granted, toads have other limitations too, so it's not a completely equivalent situation.) I don't know about you, but when I've been limited to toad movement my two reactions are: (a) "this is taking forever!" and (b) I don't want to have to go through that space".