I've used some very lightweight frames on the rear wheel trainers and haven't had a problem with hurting the bike (and I'm not lightweight).

As far as rollers they are much different than a rear wheel trainer. You not only have to balance the bike but also keep it on the rollers. Like riding down an 18" endless strip of pavement with a cliff on each side!

I've come off the rollers at speed several times over the years. Once I put a nice gouge in the drywall with my pedal. Another time a spoke caught a nut on the rollers and tweaked my wheel.

Once you get used to them you may be able to ride with no hands or even pull a sweatshirt over your head while riding. They do help balance but you can't hammer like on the road because the bike can drive off the front. You can't coast for long so you pretty much have to pedal all the time. Because you'll tend to stay more still on the rollers to maintain balance they tend to be less comfortable - half an hour is usually enough for me.

I can't read while riding rollers and so prefer the rear wheel trainers though rollers are fun once in awhile.