The portal for the Schnitzel Room looks like an Omnious Cauldron:
and its location changes every 2 hours, everytime it changes this message will appear for all the online players:
THE GREAT SCHNITZEL HAS APPEARED SOMEWHERE IN THE WORLD!
THE HUNT THE SCHNITZEL!
To find out the city where the portal is, you'll need to use the item: All Knowing Sausages 
If you don't have it, you can check all the 17 locations or ask for a friend.
(You can trade this item with the NPC Xaver
in the Orcsoberfest Island, it costs 100 Festive Points)
The Schnitzel Room can randomly appear in the next locations:




You can find more info about the mini games & rewards on: https://tibiaduality.com/evento-orcsoberfest