Crashing on (off?) rollers isn't like crashing for real.
You haven't got any momentum, because you aren't moving, so you don't really come down hard like you do on the road.
There's some awkwardness and a tremendous clattering, but really it's about like standing in the garage straddling your bike and then dumping the bike over, except that everything is a little higher, because of the height of the roller. The extra height is in an advantage, because it gives a bit more time to clip out. I've never gotten actually hurt falling from the rollers, a few scrapes, a bit of embarrassment, but that's really it. I always ride in the hall, with the wall quite close on the right. I rarely need it, but I know it's there and I can touch it if I want. The few times I've gone off, I've gotten a foot down and the bike just has tipped over and I end up straddling the bike and rollers and with a little reorganization, I'm good to go.
One time I was in the bath when Brewer crashed off the rollers in the hall and it sounded like the roof had fallen in, but he was laughing, and just got back on.
We've ended up with skid marks on the wall a few times, but they clean off rather easily.
Each day is a gift, that's why it is called the present.