ah, you mean rollers make you a better rider than trainers. I would agree, but strength has a lot to do with riding, and when it comes down to it, its almost like the machine weights vs. free weights argument. A mix of both is good. Trainer focuses the motions completely on your legs pedaling, while the rollers focus on balancing and side to side motion as well.
So, it's kind of how bodybuilders use machines sometimes to focus the weight on a specific muscle, the trainer does that while the rollers are fit for a complete riding experience.