Hi H.,
I've been there!! My boy/girl twins are almost 5 and still share a room, but it has not always been easy. When they were first born, we lived in a two bedroom house so there really wasn't a choice. It was hard because one started sleeping through the night at 4 months and the other not until he was 2...but that is for another post. When we moved into our current house with 3 bedrooms, I was pregnant again and knew that we needed a baby room, so we kept them together. Plus as you mentioned, they had always been together and I just couldn't separate them.
We had actually always separated our twins for naps even when we were in a two bedroom house. One would sleep in a pack-n-play in our room and the other in his crib. It worked well. We continued that when we moved into a bigger house.
We too started to have similar problems as you when our twins were about 2 1/2. It was very frustrating. I felt like I spent my entire evening trying to get them to sleep. So what we did when it got really bad is we did separate them and then when my son was asleep we would move him back into his room. At the time they did not like to be separated and in a way it was a punishment to separate them. As they got older and continued to nap, it was still hard. Things finally got easier when at 4 1/2 they stopped naps. They go to bed much easier now..they are tired without naps.
One thing we have always done, is after we read books to them, we give them about 15 minutes of read/play time in their rooms before we turn off the light...that has seemed to help and even if they get to bed late, they still need that time to settle in. They are definately creatures of habit.
As far as toys in their bedroom, my kids have mostly books in their room, but they do sneak a couple of toys now and then. We are lucky in that we have a separate family and living room. We turned the living room into a playroom, so all of their toys generally stay in there.
I am looking at sepatating my twins this spring when my youngest daughter is ready to move into a bed...I want my two girls to share a room. I started preparing them for this months ago by just talking to them and they are warming up to the idea, mostly because I've been letting them help me how to decide how to decorate. They are excited about having a boy room and a girl room. Although my daughter has asked me it she can sleep in her brother's room sometimes...of course I say. Your twins are much younger and I think mine are finally at an age where they can understand. Although I think it might be hardest on me when I finally do separate them :))) It is hard to explain, but I'm sure you understand...twins have a special relationship.
So, I don't know if my experience is much help, but I will tell you it does get easier. I feel things are finally starting to get easier with my two. Good Luck!!
J.