Huh... both times I played I got 3. 1 from the torturer, 1 from the cave, and 1 in Redaka's corpse. Either it's random or it's a bug.
Actually, you're quite right. I played through that bit again due to an actual bug and realised when I reloaded my game that there was another blood rose
right in front of me. Best place to hide it, I suppose. By which I mean growing in one of the mounds of festering bodies, exactly where everyone else would've expected to find it.
And as it transpired, I'd actually failed to collect the rose from the insane torture guy's lair. So there's all three of them.