I\'m currently upgrading an old rails app to use Rails 3 and Ruby 1.9.2, and RMagick is the last gem I need to install. However there doesn\'t seem to be any 1.9.2 download
I believe there are a few gotchas with RMagick and 1.9, as discussed in this thread at RubyInstaller group.
However, here you can find a post describing the steps.
Other tutorials can be found in our wiki
Hope that helps