The TBC error in a Ford F550 tells me there is a trailer braking problem. I would run a diagnostic and poll the engine control module for all of the codes that might be involved.
Quickly, though, I would say that there is a problem somewhere in the trailer wiring. It is quite possible a trailer brake connector wire has chafed and has shorted out. It is also possible that the error shows there is an error in the trailer hitch itself. Of course, this is supposing your 550 is equipped with a trailer hitch and it tows a trailer.
However, if I had to guess I’d say your vehicle does have a hitch and you do tow. I have very rarely seen a vehicle the sized of the 550 without a working hitch. However, given the error you are receiving now, I would suggest that you have the trailer hitch fixed or replaced.
As to why your truck is running roughly, I would also suggest a diagnostic and I think you will see that either the state of your vehicle’s tune is being affected and that it needs a tuneup, among other things.