Depending upon the structure of your existing theme, it will may need tweaking (i.e the user of importer) of the source database to conform with Jobroller's structure or Jobroller may need further customization to conform with your existing theme setup.
Please help our moderating team work more efficiently by not sending us support questions via PM. You can read more about how AppThemes support works
here. However, you can send a PM to follow up and remind me if I missed your support request/thread.
Thank you and have a nice day.