I have battled the boss "rooms" (necromancer, general, vampire, etc.) before and after each battle, I've been rewarded a chest and the room was then opened for playing. Tonight, i battled in the Necromancer's Crypt and was ranked first and used all 20 hits allowed in the battle - so I'm out 20 arsenal items as well. When the battle ended, I received no reward, and the boss went away. The crypt is back to the 10 keys to start another battle, so it seems that I'm not receiving an award, not going to be able to complete the quest I was trying to complete, and not playing the room -- after paying diamonds for the keys (which was a stressful decision as I hoard diamonds!) and using most of my arsenal items.
I've submitted a support ticket to GI, but to be honest I'm not sure if or how they will resolve it.