I like the idea of tying in your roll with how complete your encyclopedia is, a lot of games do something similar to that already, but you could set your initail entry's completeness to how well your initial (history)/(religion)/(xxx) roll is.
As long as you get additional rolls in the future each time you encounter [X encyclopedia things]. Possibly with a gradually increasing bonus to ensure that eventually the entry is fully complete. Or there's eventually a book/dialogue that gives you all the information.
