The processes that are necessary for roots to absorb water and minerals are as follows:
* Diffusion
*Passive transport
Both of these processes allow for a balance between the roots and external factors (soil, e.g.), and ensure that the materials are moving from a place of high concentration to low concentration. This requires the use of no energy, and makes it "priceless" to move materials into the roots. Without these two processes, plants would be deprived of nutrients and other vital substances.
I hope I helped! :)