What's the best way to memorize lots of facts?

For an upcoming history test we were given 20 terms (names, places, etc) we’ll be required to give 7–10 facts about each one on the exam. There will only be 5 terms on the exam. I’m currently trying the Roman Room system. I’m using the same room and the same objects for each subject. The only problem is remembering which things in the room go with which subject. I’ve got at least 140 facts to memorize.

I thought about having different rooms with different objects for each term, but that’s a lot of rooms to create in my mind.

Does anyone have suggestions on how I can do this more effectively?