I just bought my new Boss RC-2 Loop Station, and when I plug it into my Roland amp, I get some serious feedback. I have tried many ways to fix the problem, e.g. create distance between amp and guitar and pedal, new chords, adjust volume, etc. but nothing seems to work.

Any ideas?

Much appreciated.
Tom Morello gets feedback on purpose by going close to the amp with his guitar. So it`s about the distance between your guitar and your amp. If it`s all the way (depends on your cable but at least 5 meter/17 feet) then there`s a problem I guess. And the pedal is completely working and all?