Rollers versus Trainer...

I use them for different purposes.

Rollers require more attention -- I'm not able to watch TV at the same time because I lose focus.  I think that rollers help me work on riding a truer line and it forces me to even out my pedal stroke a little bit.  Yes, resistance isn't so much, but that's not usually my goal when I'm on the rollers.

On the trainer, I can do more with one-leg drills, harder intervals (and intervals up out of the seat), and longer rides (because I can watch TV).

I enjoy having both options -- a little variety to my indoor workout.

Heh.  Rollers are FUN.

Admittedly, my trainer is more useful.  The rollers are not very conducive to hard interval workouts.  But I used to use them on a once in awhile 30' "just ride" kind of thing.  In fact, I will probably start doing that again sometime!  They do make you sweat pretty good and you will hold a line better than anyone you know once you get the hang of them because your handling has to be pretty precise or you fall off.

Above posters are correct that you CANNOT just zone out.  In fact, I can move so little that my hands/butt go MORE numb on the rollers than they do on the trainer.  I haven't quite gotten the hang of being able to completely shift around and not fall off.  But I can ride in aero.

So, while I'm good at them I still set myself up in a doorway.   Or at least next to something I can hang onto for the once in awhile that I need it.

They are very different.

If you have any problems in the smoothness of your stroke, balance, or straightness, some time on rollers can definitely help work on those issues.

Even if you don't, they can provide a good "stroke drill" of sorts when you are just doing some base mile workouts.

For long workouts (for example 2 hours and up), it may be just too difficult to maintain attention on the rollers.

For hard workouts, you can get rollers with resistance, but it's a lot harder to push to the red line on a roller without falling, if regular hard anaerobic bursts are part of your workout

has anyone tried the inside ride rollers? they look pretty cool - though pricey 

I have both, and much prefer the rollers.  I can finally watch t.v., I can do one legged drills.  I hate my trainer and have been thinking about selling it because I only used it when I was recovery from rotator cuff surgery and needed to ride without my hands on the handle bars, although I'm working on doing that on the rollers.

The trainer made my knee hurt and it hurt my girlie parts because there is no give on the trainer.  The rollers have much more of a road feel. 

My journey was long, I didn't have sense of much balance. But riding the rollers improved my pedal stroke, my balance and I can hold a straight line forever.

But I will say, I still can't get my water bottle while riding them.