Does ROM Manager need S-OFF? I want to try the CyanogenMod9 Alpha builds for the T-Mobile myTouch 4G Slide [MT4GS/Doubleshot] and all the instructions say I need S-OFF.  The problem is that I have HBOOT 1.55 so software solutions like Revolutionary do not work and I am left with the JuopunutBear wire trick.  I am not up for that so I will stay S-ON for now.

Then, I found ROM Manager that claims to easily install custom ROMs easily, but I can not find if ROM Manager requires S-OFF for HTC devices.  Does anyone know if I can install custom ROMs through ROM Manager with S-ON?
ROM Manager doesn't do anything particularly special to install a custom ROM. It essentially makes a call to the recovery binary that allows it to save instructions for your recovery partition to run the next time it boots, thereby automating the process of flashing whatever zip file you choose. You could do the exact same thing manually.

Therefore, if your device needs to be S-OFF to flash a custom ROM from recovery, it will also need to be S-OFF in order for ROM Manager to flash a ROM. It will not work on an S-ON device since it won't be able to write to the NAND, and you won't even be able to get a custom recovery to stick in the first place, most likely, which it will ultimately need to flash the ROM.