You may need to fiddle with your LD_LIBRARY_PATH or ldconfig. I have more detail on how I got rmagick and imagemagick working under debian linux posted here:
http://lemurware.blogspot.com/2006/07/building-rmagickimagemagick-for-debian.html
Without more error information it's tough to say what might be going on. There has to be an error showing up somewhere -- are you running with script/server via WeBRICK in development mode and looking at the WeBRICK output and your development.log?
- Walter
