http://cdn.roland.com/assets/media/pdf/cube-15xl_amp_settings.pdf
I ain't a huge LedZep fan, but I'd start with the jimi setting, take out some gain, maybe a little less treble and bump the mids up a bit then play damn loud through your neck pickup. Not sure if you have the power squeezer, but try that at low volume or a hotter sound.
Sure someone will tell ya to buy a Tokai LP and a Marshall Stack...