D.B.
Hi P.,
I agree with Lisete's advice that it will just take consistency from you and your husband of walking your child back to his/her room for a while. You also need to make sure to tell your child that this is going to be changing, talk about it during the day, before bedtime. Also, you can spend time cuddling together on the couch before bed, reading books, listening to quiet music, etc. Just reinforce the idea that the couch is where you all cuddle together now, beds are for the people who's rooms they are in. You may also want to try a star chart or other reward system-Stay in your own bed all night, get a star; Get stars all week, we do something fun-ice cream, rent a movie, stay up an extra 15 minutes, etc.
I think all in all, it takes time and patience, and finding what works for your family. Hopefully some of the suggestions you get here will help! :)