This trick/technique probably won't apply to the music styles you like most, but one cool thing you can do with a room mic is use it as the only drum mic during a bridge or other transition part in the song. You can automate the mute control on the individual piece mics and mute them all at once. Compress the room mic to your liking and turn it up. This gives the drums a very different sound for a bridge/transition.
Another use for the room mic is to compress the heck out of it and mix it in to taste. You can get a bit of the loud boomy Led Zeppelin like drums this way.
Bob's comment of mixing until the room and OH's sound good on their own is also very good.