Kohei Nozaki's blog 

Recently I migrated old articles that wrote within hand made blog (?) engine to Roller. there’s a useful Groovy script that placed in source distribution of Roller. I referenced that script and created a standalone Java program which imports entries that saved as RSS 2.0 XML. the program is intended to use with WordPress WXR file but I’ve never used it with real WXR file which WordPress produced because I don’t have any WordPress instances for my own. I used it for a XML file which produced by Rome and before import I added some tweak by hand.

I think it’s harder to use without any modification but it may be helpful for someone wants to import entries with API for Roller, so I pushed the program into GitHub.