I just tested it on IAP running 6.5.4.4. Yes the knob goes back to unrestricted, however if you move it back to Role based, & click on the role, you would see the bandwidth contract in place.
If you SSH into IAP and do a show run, you can see something like:
wlan access-rule "SSID1"
index 3
rule any any match any any any permit
bandwidth-limit downstream 4
bandwidth-limit upstream 2
So definitely the config is getting saved, atleast on the latest version.
But why did the slider move back to unrestricted?
I will get a bug filed for it.