Have you checked your environment variables?
I had something similar, and had to go and manually change the JAVA_HOME variable to point at the 64-bit JDK instead of the 32-bit one.
Did you download the 220.127.116.11 RhoMobile suite installer? If so, you do not need to install Ruby or any other dependencies as we package them all in the installer. Also the only dependency that you will need to run RhoMobile Suite will be a JVM.
If you need more help, please reply to this or contact me at firstname.lastname@example.org
You should execute "gem install" command for rhomobile-debug, rhodes-translator, mspec, rhodes, eventmachine, rhoconnect, rhoconnect-adapters, rhoelements, rhohub gems.
Or use prepackaged RMS which goes with all installed gems.
I'm using windows 7 64bits and I didn't have any problems. I'm using JDK 1.6 for 32bits.
Try to type in the console the following command to see whether your JDK is properly installed.