Could the bosses once again drop the room spell scrolls?|
They were super rare back in the day. I'd say maybe 1-5 drop(s) per day maybe?
You could make the most frequently travelled one (aka Bears - Kugnae) have the least impactful room one - room para.
Then put the more impactful ones into the caves less traveled, I'd say the Buyan one is the least (could have room whirlwind) and followed by Nagnang (could have room lethal strike) then the moderately travelled Wilderness (could have room scourge).
Another way for you to control or restrict how many of these items get accumulated is adjusting the spawn rate of the boss. You could say it would only spawn once every 3 hours (so even at a 100% drop rate there could only ever be 8 per tier per day).
All for a lost Cause.