Here's something we used to play over 20 years ago - hope it gives you a few ideas.
We used to use the old Heroquest board but place out a number of tokens to 1 side so you couldn't see what they were (they were shuffled 1st so that no-one ,not even the evil player knew what they were) Certain rooms upon the questmap were then allocated as RANDOM.
Once a character entered a RANDOM area a token was then turned over to reveal its' number then the evil player would check his notes where further random events would take place (eg. an inn where you could buy drinks, play a game of chance to gain money , or get involved with the local drunkards, check out quests offered by patrons, etc - the list is endless...)
Anyway, have fun ,
That's a nice idea. I had a similar idea with card deck with "events".
Whenever the Evil player had no monsters on his turn (nothing to do) he would draw an event card, which could spawn a monster, a trap, a treasure, etc. Never finished it though, but it's on my meandering list of to do stuff :P
Your idea is great for quests that don't have many rooms or if you're playing through the quests a second time.
You could do the same with a die roll though (d20 with a list of 20 events or rooms for example)
The only difference is that a die roll may spawn the same event twice, while a card or token deck can be used for one time events of you discard the cards/tokens after use.