Mr C. Yes it will help break down the roots.
Mr TR is also correct but there can be problems if pathogens are present and can reproduce unchallenged.
After removing the root ball from the previous grow i break up the media removing the larger roots and replant.
I use an enzyme in conjunction with a multi-strain bacteria/fungi, this will create your own little multi strain clean up/protection crew.
This crew of microbes will feed on dead root material, outcompete, antagonize and even prey upon unwanted pathogens.
Many symbiotic relationships between the new roots and microbes will be fostered, offering further protection from pathogens. The process will feed itself and your plants.
I use rockwool and I can re-use the media 4-5 times using this method.
Regular flushing becomes very important as the waste products from this process will make the media very acidic if left.