When they are ready...we moved our DS to toddler bed in the same room at the age of 3.5yrs, later at 5yrs we moved him into his room
Does your kid go to sleep without you sleeping too? If so, he/she is ready to sleep alone. We moved my son to his own room when he was 10 months old - We waited this long simply because we previously did not have the space to move him out.
I started putting DS in a separate room in his bed for the afternoon naps first when he was 5! Slowly, I moved him to his room on nights - but left the door open - invariably, he would rush to our room by 11-11:30 midnight - slowly, by the time he was 7, he came to our room every night between 3:00-4:00 am! Now he is 10, he comes to sleep in our room very rarely - at about 5-5:30 am! Only when he has nightmares !
It depends ....few kids start early stage..few takes time. Usually 5-6 is the age when kids should start to use their own room....going towards independence.. My DS started at the age of 6-6.5 Only hiccup is he gets up early when he sleeps alone....like 5.30 -6 am
We put them in the other room together when the elder one was 3 and the younger was one. We let them sleep together in the other room in the afternoon. Even at night ,we put them on half the bed and we slept on the other half. Since they were together ...it wasn't a big problem.