root without reflashing

OK I have a rom I like but don't have root(su). Can anyone post a script that will run on boot to put su in the system/bin and change the permissions? I don't want another custom rom, just that one script to run. Or if you could tell me how to create a custom boot script like the ones that start the upgrade process I could try. I thought putting a scriptcmd on there would work but it didn't fire (yes I used mkimage to create it)

 

I have already tried this and other root/softroot apps, none of them worked. I am using the wmt2x series rom (only one that actually loads fully). I know that the boot scripting has root capabilities as that is needed to re-flash the rom, and I know you can run script at that time (again because of custom re-flashing). I have even built the script needed to accomplish the task, but it won't fire. I really need to know how to fire off script during boot (script folder), I put my scriptcmd (created with mkimage) in the script folder with su and superuser.apk but the script is not firing. Does anyone know what else I need in the folder to cause the script to fire? I just want this one script to fire, not the full firmware flash.

 

so nobody has any ideas? seems like you would have to know this to build a custom firmwire