Wow, I am sometimes appalled at some of the responses that moms on here get from other moms that are very old-fashioned and close-minded to more modern parenting techniques. Take their advice with a grain of salt... You have done a wonderfl job so far and have given your son a wonderful gift of being able to sleep with you for his first 2 years. You have created such a close, strong bond and relationship that you may not realize, but would have not been possible with him far away from you, alone at night. Pat yourself on the back...
I would recommend making the transition and calm and gradual as possible, so as not to cause alot of insecurity and loss of closeness and trust in you. No punishment, criticism, getting upset and try to be understanding to his emotions, frustration and confusion as to why now this is changing. Remember that in his eyes, he is being pushed away. Treat it more like a 'graduation' or reward that he gets his own room, bed, sheets, pillow, nite-lite, etc...and although these may seem great to us, he may still feel scared and alone. Maybe sleep in there on an air mattress for a while until he is comfy or start even slower with him in a bed in your room, then move it to his room after a few months. Slow and gradual will usually be easier, rather than a battle for all.
I wish you all the best...and pray for keeping a super relationship through the transition. Alot of kids aren't ready for their own bed till about 3, so go slow!