Found this thread of mine from the summer of 2009!
I realize the answer was never written here so here goes as the info is still the same and will be of use to any other current querents
➊ There is no way to export to wav on Rosegarden ... you export to midi and then ...
➋ One needs to use Timidity
Code:
timidity -A120 filename.mid -Ow2 -o filename.wav
➌ If you want 24-bit
Code:
timidity --output-24bit -A120 filename.mid -Ow -o filename.wav