Do you tend to go for characters of your own sex?

Yes. If I get the option to customize my own character, then I'll model it after myself or anime/manga characters I've created. Whether the character is a male or female really doesn't matter as long as I can associate with the character. There are many factors that contribute to it as well.

Do you think characters of your opposite sex don't, or do, suit roles for particular reasons?

Female characters suit their roles as long as they are strong, independent, and don't objectify women in ways that can embarrass them or drive them away from video games.

Have you ever noticed/ known somebody that won't play as the opposite sex?

No. It doesn't matter to my friends as long as they can play the game.