I think like anything, going to the dentist, weaning, co-sleeping - it has to be done slowly and gently. Make a big deal of it and they are going to be less likely to want to do it, become frightened of it etc.

What we did for Marisa was make her bedroom a special place for her. We bought her new sheets in her favourite characters / colours, made a theme in her room with her favourite things, and made sure the room had plenty of fun things and fun times were spent in it.

Some people do things like hanging special things around the windows like crepe paper, put their paintings on the walls, make mobiles with their favourite theme things, hung photos of family, etc. But lots of little things that help them feel that it's their part of the world. Kiddie beanbags, a work desk, and most of all, not sending them to their room in a way which they will not enjoy it - Marisa has 'quiet time' in her room when she needs to or if she needs to calm down, but we don't make it such that it's the 'naughty room' or 'naughty corner' which only emphasises the behaviour and that it's a place to go when she is bad. So try making the bedroom a fun place, do some fun things in there with him and he'll start falling in love with his room sometime soon I am sure. Slowly does it, it wont be overnight but the more fun you make it, the easier it will be, than having a power struggle with them. Marisa was a co-sleeper from birth and she still jumps in every now and again, but she is fine by herself too - so even the long time co-sleeping babies can get the confidence to move into their own bed themselves.