well,, it depends on what exactly your trying/wanting to do with it among alot of other aspects...what style of music u wanna make, or are u more of a player type thing?... your personal taste for sounds, and what kind of set-up you plan on having...(will you be using it into your comp. via MIDI etc.)...stuff like that u obviously need to consider, and take your time selecting....dont jump into buying something real quick, look around....
Depending on what store you go to and your luck of the draw in a salesperson Id just spend some time chatting with them, they're usually knowledgable..... play around on any gear before u buy it, read magazines, etc......
and oh yeah.....dont buy a Roland

unless its one of the more expensive pieces-
P.S- check out [url]DigiBid.com[/url] if u decide maybe u wanna buy used after u find out what u want....I've nevr avtually ordered anything, but Ive seen some good deals there