I'm aware that Risa Ohki sang the "la mia tristezza (which is the theme of sadness)" and "La passione commuove la storia (I don't know what that means)" from the Genso Suikoden Vocal Collection. The other tracks on that CD are done by some vocalist that Risa Ohki easily out-classes, in my opinion. She may have performed in the other Suikoden vocal collection (for I'm only aware of one other . . .) but I don't know if she's in it or not.
I'm also not aware of any official page for her - at least, anything in English. I'm considering making a fan site for her, though it wouldn't have much to offer besides a point on the internet where I could potentially gather more information about her.