I ordered the Rotoworld magazine and it seems ok. It would have been a lot better if they did not load it up with ads. And it is not really designed for fantasy rookies (the layout is not as appealing as other magazines).
Nonetheless, their player write-ups and team by team analysis are well written and helpful.
I am running a league for fantasy rookies this year. One of them picked up a magazine and had me preview it. The layout was very simplistic and perfect for owners who just want to become associated with baseball's player pool.
Its name was something basic like, Fantasy Baseball Guide 2004: Expert Edition. I can double check that when I get home.
If you are just looking to get a basic start to an introduction to baseball's player pool, it would not hurt to pick up some magazine that looks good to you.
Like hooligan1 said, make sure to check some fresher sources, as the magazines will quickly become outdated in many cases (ex. Guardado is no longer merely a $11 reliever