In Rosegarden 12.04 there's a bug in midi export function. It usually doesn't happen in all tracks and channels but almost always happens in one of them. When you export a midi file the first note of the track is exported as a midi event before the first program change and first controllers events. This results in the first note of that track being played with a wrong instrument, wrong volume and another settings that inside Rosegarden were regulated on the special parameters panel.
This may be noticed when the midi file is played or opened in another softwares.
For example, you may download Midi Locator (it's a shareware for Windows but also runs on Linux under Wine) or some similar software, open the midi file and see the list of events that the first note of some of the tracks will usually be list before the first program and control changes.
I have tried different builds of Rosegarden 12.04 in different operating system and found the same bug in them. That didn't happen in the previous version.
Please, give attention to this bug cause it prevents users from having a midi file exported correctly. Meanwhile it also has not been possible to use Rosegarden as the only sequencer to build a file because the only way to correct the bug in the midi file is using another midi editors.