If my budget (and space) were unlimited I'd have both rollers and a high end fluid trainer. Rollers are more pleasant to ride, better for the bike, teach you good form, provide decent resistance and I find I can ride them longer. Cyclops or similar high end trainers excel at maximum strength sprint intervals which you may not want to do on the road.

I try and get out on my bike regardless of the weather, but when I'm stuck inside, it's rollers for me.