I would like to start shooting RAW instead of jpeg. I am wondering if i need to still worry about setting ISO, aperture and shutter speed. If so, why?
Yes. You still need an exposure. RAW is not magical, it is just the sensor data for a certain exposure.
You must choose the aperture according to the depth-of-field you want, the shutter-speed according to the motion you want to capture and the ISO to balance between them which will set the gain on the sensor to make a balanced exposure. Sure, RAW is more permissive if you do not get it perfect but anything clipped on either side is gone forever.
Of course, you can let the camera choose some for you in a automatic or semi-automatic mode but it will still choose an exposure which determines way get captured and therefore what gets stored in the RAW file.