5.6. What does "System timer resolution is too low" mean?
If you see this message in an error dialog when Rosegarden starts up, then you are probably using a Linux kernel that doesn't offer sufficiently high-resolution system timers for MIDI use.
Rosegarden uses ALSA sequencer queue scheduling (inside the Linux kernel) for its MIDI output. The sequencer queue can use a variety of timing sources, of which the default is the kernel system timer. The kernel system timer was 1000 Hz in Linux 2.6 kernels up to 2.6.12, but as of 2.6.13 it's now 250 Hz in mainline kernels. This is not good enough for good MIDI timing.
Your options are:
Switch the sequencer to use a different timing source (Settings -> Configure Rosegarden... -> Sequencer -> Synchronisation). The best one in theory is the RTC timer, which is only available if you have snd-rtctimer loaded, but unfortunately that has a habit of totally locking systems running real-time kernels. Meanwhile, the PCM timers only work if the JACK audio server is running, and suffer jitter corresponding to the JACK buffer size.
Recompile your kernel with system timer set to 1000 Hz. Sadly there's no way to change this without a recompile. It's the best solution though.
Switch to a different Linux distribution that provides a kernel more appropriate for multimedia use.
Put up with the poorer timing of a 250 Hz timer (if you want to get rid of the warning while continuing to use this timer, set the timer source to "system timer" rather than "(auto)").