Jobroller is a theme too and not a plugin. One way to do that is modify Jobroller to look like your existing theme however this will require serious code customization. If you are not a programmer, an assistance from an experience coder will help you accomplish such.
Another workaround is to install an instance of wordpress with Jobroller on the subdomain so you can still maintain the look of your main existing site.
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.
