The roots are a secondary root system and the blue green algae that inoculates the roots are having the symbiotic relationship with the cycad. If there is no blue green color on the roots, they may not be fixing much nitrogen. If you fertilize the plant at all, I would not worry about what is happening to the roots. The amount of nitrogen being produced is very low in comparison to using fertilizer. It is better than nothing, as it would be out in the wild while growing in sand or on rock, but fertilizing works way better.