You've talked to Lieutenant Luis already, I assume? Did you read all the wanted posters on the sign to the left of the stairs leading up to where Captain Rodney should be? Did you talk to Palmer in the barracks?
I don't know what the internal name for Captain Rodney is (probably tried all the obvious permutations that you did).
Did you try starting a new character, doing the minimum in Farglow and seeing if Rodney shows up once you get to Broken Valley? Maybe try verifying local files for the game first, if you didn't already do so.
Do you want to try emailing me your save (raze@larian.com) to see if it works here? If not I can forward it to support (support@larian.com), or you can do so yourself.
In XP the saves are in the folder
C:\Documents and Settings\ %username% \Local Settings\Application Data\Divinity 2\Savegames
or in Vista / Win 7
C:\Users\ %username% \AppData\Local\Divinity 2\Savegames
You may need to set Windows Explorer to show hidden files and folders (
XP, Vista,
Win 7).