Here's a couple that I think would be great to have on my Roku:
KBOO Community Radio - based out of Portland OR. Great music programming and lots of locally produced public affairs content. They've been around since 1968.
They are on the web at http://kboo.fm
and their webstream (128kbps) is http://live.kboo.fm:800/high
Another is DFM RTV International, which originates out of the Netherlands, but has programmers streaming from all over the world 24 hours.
They are at www.dfm.nu
and their stream is http://126.96.36.199/dfm_1