Root access restriction
 

Is it possible to disable root access from wlan0? Is it configuration issue?

no, that's not possible, they are operating at too many different levels there. there are certainly ways to get what you want i expect, but not in such a direct manner. if your wireless interface is on a different network then you can use /etc/hosts.allow or /etc/hosts.deny to prevent access from those ranges. also within certain servers, e.g. sshd you can prevent certain users from certain source addresses.