This is an old thread, but I am back to this issue in a slightly different environment. I am now S-OFF with bootloader locked. I installed the latest stock Sprint RUU and lost my root.
How can I root it without unlocking the bootloader with HTCDev (I would prefer to keep the stock recovery too)?
I was able to do it with the RUU/zip method. I packaged my custom recovery image into a zip and an android info file then flashed it. Once the custom recovery was in, I could use it to flash SuperSU. I then flashed back the original recovery using the same method.