Tonight for the first time I realized that all my posts to JRoller and Blogger are all just present on their respective websites, but not as a copy on my local machine or some other backup. While I have full trust in Google's engineers to keep Blogger up and running as well as my data safe, it is never a bad idea to make a copy of your stuff.
So I just googled for "Blogger Backup" and found just that: A Blogger Backup tool. It is a .NET based tool that utilizes Google's C# data access libraries. Probably it would have worked with Mono, but as I had a VirtualBox'ed XP instance up anyway I used it there.
Once I had downloaded and installed the tool, it was just a matter of a few clicks to get all my posts saved in Atom/XML files locally. One thing has to be noted though: Make sure your blog feed is set to "Full posts", not just the summary. I first got this wrong, so all the backup files just contained at most the first paragraph.
Now all 99 posts I posted to my blog reside in a local disk folder which makes me feel a little better :)
As for JRoller I so far have only found some special template based backup ideas, however none look really too appealing. Maybe I will just use a website grabber to snapshot the whole thing as HTML.