I haven't tried Rohypnol but I've heard I shouldn't necessarily believe all the hype. Flurazepam I've tried a few times, and though I found it pleasant, I didn't think they were that powerful at all. They were hypnotic and helped me get to sleep, but didn't feel outright sedative when I didn't go to sleep on them (which nitrazepam, for instance, did).
I don't know how practical they'd be (atr me) for insomnia, though; a 15-30mg dose didn't seem quite enough to put me to sleep, but taking larger amounts would probably lead to accumulation at some point after a few nights' dosing, as it has active metabolites with a half-life of up to 250 hours.
The next time I run into these, I might try IVing them, as flurazepam is apparently water-soluble and they come in capsules.