My twins too had always shared a room up until last year. Naps and schedule all play a part of this as well as just the natrual personality of your two. We lived in a very small house when they were small (they are now 6) and only had two bedrooms. We ended up setting up a pack n play in our room and would put one to bed in there and the other in their room. Then move the one in our room once they were asleep. We had to do this until they were just over two for night time sleep...we continued it for naps because that seemed to be more of an issue then night time.
Are they still in a crib? We kept ours in their cribs until they were 3 (they never climbed out...) and that made a huge difference. Also, not sure what your schedule is like during the day, but an earlier bedtime may help. I know that may sound crazy, but I think it really does work.
I agree with the person who said put them to bed earlier and give them some play time before lights out. We started this with our kids when they were about two. We would read a few books together and then give them about 15 minutes to "read" before the lights went out. We did not supervise this "reading" and let them do what they wanted as long as they were in their room and no one was getting hurt. We still do this now.
Most of all...enjoy every minute. It goes fast and before you know it they will be off to school. It is a hard first few years, but I can say with mine being 6 I am finally seeing the light at the end of the tunnel...they are at such a great age.