From another thread, I know you'll be sending your site credentials. We may need to see this happening to understand specifically what redirect needs to be changed.
For Rokbox popups, specifically, we added the ability to have a custom image because the default (javascript based) Login With Facebook button wouldn't work in Rokbox pop-ups. However, with the custom image login buttons, we haven't heard of other issues with Rokbox, so hopefully seeing it in action will make it more clear.
For more information about the custom image stuff I was talking about, see the 2nd and 3rd question on the page below:
www.sourcecoast.com/jfbconnect/docs/common-support-questions
Alex