So I got my AllShare Cast in the mail today, and trying to connect it I constantly got the connection error
After about 20 min of unsuccesful attempts, i decided to tap and hold the line that showed the name of the allshare cast dongle on my S4. I got the screen allowing me to connect using PIN.
After the dongle generated the pin and I punched in on my device, it connected with no issues. So it is possible to use allshare cast with rooted devices without too much hassle. Granted you should be on stock rom and kernel.