If you could increase your dissolved oxygen at closer to 68*F you’d have even more amazing results. Root rot happens because of not enough dissolved oxygen in the water. You could increase aeration to get more O2 in the water.
It is a known fact that the cellular metabolism slows a lot below 61*F. But if it works for you, as they say, if it ain’t broke, don’t fix it.
If you gave me some more info, I might be able to figure out why you are getting root rot, or not having enough dissolved O2 in the water at slightly higher temperatures.
Are you supplementing your crop with CO2 also?