Hi,
I think you might want to use some shuffling or helper storage, to avoid getting into the same room twice. Two ways (there are certainly more):
1) create array of size 250
2) fill it with consecutive integers
3) shuffle random pairs of a hundred or more times
4) make the player go from room to room, according to the (shuffled) order of elements in your array.
Way #2:
1- draw random integer as in examples you've seen above
2- if integer is already in the helper container (#3 below), repeat drawing
3- store the number in a helper array/string etc
4- proceed to the selected layout
Hope it helps,
Greg