There no "right" choice of how many starters you need, but the decision is influenced by how often you can change your lineups, whether you're required to use a certain minimum/ maximum number of starters or relievers, and above all, what your league's games and/or innings limit is.
How your pitching shapes up depends also on how many teams there are in your league, but even if it's only ten, your guys look pretty good. The Big Unit alone will practically guarantee you'll climb out of the pitching cellar very soon. Glavine and Radke are solid, I like Padilla (even though he'll go through some rough spots), Ishii is the big unknown factor (see the Ishii Watch thread). I'm not too high on Castillo, but he's a serviceable 5th starter. I also don't like both Mays and Miller as much as most fantasy folks do, but that's just my minority opinion. Of the two, I like Miller more, if only because Mays might miss a lot of time.
Anderson and Graves are both very valuable - if you can pick them up, you won't regret it.
Of Romero, Dotel and F-Rod, I'd normally go with F-Rod, but since you have Wagner, who is struggling, Dotel sounds better: solid stats plus insurance.
Anyway, let us know your league settings. In most scenarios, though, this looks like at least an average pitching staff, and probably a good deal more than that.