I've been struggling with getting my One S-off for a few days now, I've searched the forums but there is so much information that it's next to impossible to wade through it and find what you are looking for.
Here is what I did:
I got the HTCDEV unlock and ran it, I installed CWM and rooted it. I kept getting the Root access not available error on both RumRunner and FireWater.
I flashed CM11 thinking it might fix it, Nothing.
This morning I just started looking and I found the solution.
Go to SuperUser app and select Settings-->SuperUser Access --> Apps and ADB.
Then follow the steps for either Firewater or RumRunner and It should solve your problem.