Among seven roles I heard her in, only ONE female character appeared; all others were those of young men (and bishounen, each of them - three with big green eyes, and two with big blue eyes). However, according to ANN, there are many more female characters voiced by that seiyuu.
Mitsuki Saiga was born in 1973, Dec 12, and lives in Saitama. In the pictures, she (I struggle not to write 'it' -_-') is a completely flat-chested person, and I even heard her singing in definitely male voice. But, ah, let it be.
The very first role of Saiga I heard was Maria Ross from "Fullmetal Alchemist" in 2008. However, it was the aforementioned only female role of her, so I didn't pay attention to the voice at all. It was only January 2010 that I really NOTICED her, and it happened in "07-GHOST", where she portrayed the main hero, Teito Klein. "07-GHOST" is one of my most favourite anime ever, and thus Teito's voice was pretty much imprinted in my head (especially after watching the anime, say, five times in a few months), not to mention I really like and appreciate the character himself. It is funny that she also played a main character in the next anime that had an equally great impact on me, and it happened in December 2011, so after TWO years.
In the meantime, however, I watched two other anime with Saiga as main/supporter character. She portrayed Kouseki Ryoutou in "Koutetsu Sangokushi", a hot-headed, self-proclaimed 'little brother' of the main (utterly boring) hero, and a son of general, who later becomes one of the pillars of the country. I must say I liked Ryoutou a lot, but then again I liked literally all characters in "Koutetsu Sangokushi" but the main hero -_-' Ryoutou is not really a child any more, yet not an adult yet; he is extremely loyal and good-natured, even though he sometimes struggle with his feelings; he is a playful young man and a skilled warrior.
As for Wolfram von Bielefeld in "Kyou Kara Maou!", he was probably the biggest surprise. Well, the biggest surprise was that I took such a liking to him. Wolfram, a noble youth, called by his older brothers a "selfish prince", is aloof, haughty, sometimes mean and definitely disrespectful, and he pretty easily gets upset. However, during the course of the anime, Wolfram becomes extremely loyal and sturdy, and he shows an admirable constancy of his feelings. At the beginning, I would have never expected myself to come to liking that character so much.
"Toward the Terra", watched in late 2011, made my head blow up. I found it the most emotional anime since "07-GHOST". And what a surprise, Mitsuki Saiga played a main character here, too. I probably find Jomy Marcus Shin the best role of her, and I admired the way she played him. At first, Jomy is an irresponsible and defiant teenager who later becomes a wise leader. Together with his main adversary Keith Anyan (voiced by Takehito Koyasu), they created a splendid duet, with Keith attacking and Jomy persuading, to reach a wonderful conclusion. I recommend "Toward the Terra" to everyone!
Recently, I heard Saiga in three roles. Well, the first of them isn't really a role, as she provided a narration to "Sengoku Basara: Judge End" (a very nice hearing, really). Then came Kakyou in "Tsubasa Tokyo Revelations", a minor role but very pleasant. (Kakyou is my Top 3 characters in "X", so I'm always particular about him, although here he was rather anaemic.) But it is in "Kuragehime" that Saiga performed a role that may be seen as the very best icon of her voice-actor career: Kuranosuke Koibuchi, a young man who pretends to be a woman, mostly through wearing female's clothes, wigs and a heavy make-up. They couldn't have found a better seiyuu for this character :D
As shown above, all of my encounters with Mitsuki Saiga were very positive and some of them even very meaningful. Thus, I have a lot of sympathy for that seiyuu and find it enjoyable whenever I can listen to her voice.