Welcome to Ironworks MuffinGirl!
Anyway, inside the slime room, did you kill the giant serpent? Either on its body or in the giant vat of slime in the middle of the room, is the Slime Scepter. This will open more of the doors, like the one to the Ice room. The new scepters are usually found on the boss of each room.
Slime: Giant Snake (Kill by using fan to blow slime gas from room)
Ice: Ice Golem (Kill by blowing slime gas into the ice room, then attacking)
Fire: Fire Giant (Kill by luring fire elementals into the Ice Room so they freeze, then attacking Fire Giant)
I think this should help some, good luck!
-Brainless One