I would imagine that it will be modified by movement skills, which we don't really have any options for at the moment apart from Blink. So every character gets the dodge roll as a base, or you add a movement skill gem that takes it's place and comes with it's own benefits/downsides.
If they don't go down that route then I wonder whether a double tap mechanic would work, single tap gives you the short roll now with better I frames, double tap roll covers much greater distance but has a short cooldown afterwards so that it's not spammable and there's an element of risk with positioning etc.
Early days yet anyway, plenty of time to experiment.