Rosegarden cannot handle recording very complex music such as the attached excerpt from the third movement of Beethoven's Moonlight Sonata.
Before running the test, listen to the attached MIDI file to get an idea of what constitutes "correct". Then you'll be ready for the test...
Start from a clean slate with File > New. Go to Composition > Change Composition Start and End... and set the end to 500 bars. Set up rg to record on three tracks. Set the first track to filter channel 3, the second to filter channel 4, and the third (you guessed it) to filter channel 5. Arm all three tracks for record. Start recording. Use aplaymidi (or pmidi) to play the attached .mid file into rosegarden's record input. Once complete, stop rg. Now play what rg recorded back. It will not be correct. Most obviously, some notes in the rolled chords will have the wrong velocities, and the part at the very end where the melody comes back in is completely mangled by missing notes. (The effect is even more pronounced with the MIDI file of the complete piece. It's as if the problems build up as the recording progresses.)
Thanks to Aere Greenway for finding this and providing the test MIDI file.