Ok. I have search through timidity manual using man -t timidity. The -E option seem to be what I need. It can enable/disable several features as portamento, vibrato, delay, reverb, chorus. But what really seems to be missing is a way to enable/disable attack, brightness, decay and release. These features are important for the quality of playback. Timidity windows gui handles them very nicely. But I found nothing about it on timidity manual.
AS for Rosegarden I tried to use qsynth as output and these controllers take effect on it, what proofs that rosegarden send these events out. But the response of qsynth to them is very limited. The timidity responds much better.
There's a workaround. I may place these controller on the file generated by rosegarden, export as midi and play in timidity windows gui. That's what I use to od. The only issue is that while composing inside rosegarden I can't hear the real result.
 
Fernando Martin