Rooted, then flashed, now not able to root again /system is always read-only I rooted my Android ICS with some script.
It was rooted then I installed and removed some system application.
Then I formatted the device and re-installed the ICS.

Now when I try to root it again it gives error could not copy are you a root?
I searched for that and finally found that though I re-flashed it any times.
/system is read-only.
So then after I tried 

adb shell
mount


then command of mount and it gives error permission denied.
Please help to reset the permission of /system so I can manually add the su file in it.

The technique i used to Root is at this link.
Then i format using cwm and install new rom. Now i am not able to root it.
I have posted the question on same link shown in question. Till that i tried everything format SD card totally, also tried different roms of ICS still it was not worked. 

Then as in reply i got on that forum saying install gingerbread rom then root it, use OTA root keeper and upgrade. 

So i did similar to that i installed gingerbread.

Then i formatted all using cwm. Then i installed new ICS refrec v2 rom. And then after i tried to root it. And it worked.
Hope so if anyone face the same problem they can downgrade to GB then again move to ICS to root it after flash if their favorite rom doesn't come rooted. :)