For me, rollers are for when you can't or won't ride outside.
If you have to ride inside, you can be on a fixed trainer or rollers.
A fixed trainer is like pedals on a box. There's no feeling of anything except resistance. Sure, augment with Zwifty-games or whatever, but you get your workout with minimal fun.
Rollers change the indoor game because you have to actually balance and focus. I could "almost sleep" on my fixed trainer, eyes closed, earphones singing, lights off, whatever.
Rollers, you can fall off. Of course, there's no forward momentum, so when you fall off, you fall off sideways. And if you're clipped-in, you're probably going down fairly hard.
Rollers make you constantly pay attention to keeping the bike on line, and there's something to that which some folks in this discussion aren't acknowledging. And, yes, that in itself can/may/might improve the skills of a rider.
But you still just keep staring at that wall in front of you. Boooooring, but better than fixed trainer for me.