If you have root then you can indeed use the desire camera and you don't need to use the desire rom. I would recommend using Cyanogens rom and adding the camera on top of that.
The desire camera has touch to focus and a slider to focus in and out.
I've been using it for some time now and LOVE IT!!!!
Link to the Desire Camera on the XDA forums:
[MOD] Desire Camera R2 Based on various kernel mods - xda-developers
Good luck!