Rollers are great, but inexpensive rollers have no friction, or load adjustments to make your work out harder. Also rollers are more difficult to master, requiring careful balancing, which is good if you want to learn to balance a bike better but bad if you make a mistake and fly off the roller at full tilt to the rear wheel and find your self crashing head on into whatever is in front of you!!!
YouTube - Chet's Roller Crash and:
YouTube - Sad first time on Rollers Both of these are low speed crashes so they just fell off the side but you can see what your getting yourself into.
Trainers are far easier, less expensive and you can get new ones for under $200 like this one on sale, that I own, and is highly reviewed:
CycleOps Fluid2 Cycling Trainer New - offers - Bing Shopping