Limit "write to author" to certain roles

I know you can prevent the write to author link from appearing on particular content types.
But is there any way to control the link so it is only accessible to certain roles?

Also is it possible to ensure that for some content types the link is available to all roles, but on other content types it is only available to specific roles?

I guess the best way of doing this would be through theming in template.php. An if statement could be written which checks the content type and role and then show hides the link accordingly.
However, I'm not sure how to do this.

Could someone give me some hints or pointers.