Rosegarden does not give its full potential if used with the JACK sound server (must sound system on Linux), but works with restrictions on anything.
Rosegarden itself is fairly simple to configure, the problems come from a variety of audio and MIDI management on Linux, difficult to understand for a beginner.
Online help on the website of rosegarden ( http://www.rosegardenmusic.com/resources/ ) and https://linuxmao.org are satisfactory. We can easily see if the software meets their needs, skills ... before embarking on the adventure.
I use rosegarden on many computers, ranging from the AMD K62 350 MHz to 3 GHz P4. If it is limited to MIDI, rosegarden runs on modest configurations, provided you have at least 192 MB of RAM. The performance of the whole are very good, and stability is by appointment. In case of crash (common in experimental versions of the software), a self-protection works.
I use rosegarden 4 in three years, and even before I was using another version, much simpler (but just to create MIDI files).
I particularly like the score editor of Rosegarden 4, very powerful and very intuitive: it can import and export MIDI in his scores, but also in various formats (to include the scores in print), including Lilypond in (for beautiful partitions "engraved")) and even in Csound (for gurus of contemporary music). on the other hand, support for recording audio is not (yet, but it is improving) the fort of Rosegarden. You have to use free software Ardour for this work.
I was disappointed by other tools under windows (high price volatility), including quartz. The price / quality ratio is excellent, of course (free and free). There is a commercial solution at low cost ( Studio To Go! ( http://www.studio-to-go.com/ ) ) including rosegarden as flagship software, but I have not tried because the main advantage of this system is to make easier the use of VST (i) which I do am using it. I would do, of course, this choice-I 'm happy, and as it is free software, we are not a prisoner!