The ROKR is a
joke of a deadend: 100-song limit, regardless of memory. the clickwheel thingy (aka the ipod interface) is gone; Cellphone battery life; no, you have to buy your ringtones separately -- you can't use any music you download for that;
So buy your nano or a decent mp3 player, and keep your phone separate.
Or, if you must, buy someone else's phone mp3 player. they've been around for a while and aren't intentionally crippled like the ROKR.