Our daughter always had her own room from the day we brought her home. I didn't want to have to go through what friends had, with bubs not sleeping in their own room and wanting to be with them ALL the time. She slept in a bassinet until she was nearly 5 months old and took to the cot so easily. We must've had a big bassinet as everyone kept commenting that she must be too big for it by now, but she still had room to stretch her arms to the side and not touch them. We only put her in the cot when we did, so we could make room for her ever growing stash of toys and things.
Its really just what you feel, as everything is with being parents. Some bubs who are nearly 1 still sleep in their parents room, in a cot, and everyones happy.
Lisa, SA, baby girl (4.5.03)