There's nothing like that in the commands like. You can easily write your own though, just open a .cs file, should do the server.cs, and put in something like
function serverCmdAnnounce(%client,%msg0,%msg1,%msg2,%msg3,%msg4,%msg5,%msg6,%msg7,%msg8,%msg9,%msg10,%msg11,%msg12,%msg13,%msg14,%msg15,%msg16,%msg17,%msg18,%msg19,%msg20)
{
if(!%client.SuperAdmin)
return;
for(%i=0;%i<20;%i++)
{
%msg=%msg[%i];
}
messageAll("\c3"@%client.name@"\c6:"SPC%msg);
}
Then you can do /announce blah blah you all suck at this game up to 21 words.
Results may vary if I screwed this up with an error.