Not sure about the addon, but it could be scripted fairly easy
function serverAnnouncement() {
$announcementRandom = getRandom(0,2);
if($announcementRandom == 0) {
announce("announcement #1");
} else if(announcementRandom == 1) {
announce("announcement #2");
} else if(announcementRandom == 2) {
announce("announcement #3");
}
schedule(30000,0,serverAnnouncement);
serverAnnouncement();
}
serverAnnouncement();
Iirc that's how it'd work, although I'm relatively new to Torque.
To set the announcements just replace the "announcement #" phrases with your announcements (although keep the quotation marks)