G.N.
My son does the same thing, I let him fall asleep on the couch and then I carry him to his bed, I have a gate at his door so he cant get out of his room. He sometimes wakes in the early morning but I just go in his room and lay down with him (he is in a fullsize bed)until he falls back to sleep. I never got in the habit of having him sleeping in our bed.
Or you can just walk him back to his room tell him he needs to sleep in his big boy bed and tuck him in and kiss him nite say mommy loves you, do it a second time tell him the same thing kiss him goodnite and leave. If he does it a third time just walk him back kiss him goodnite say I love you and walk out. Keep doing it until he gets the idea that he needs to sleep in his own bed. Maybe need to put a gate up in his room to keep him in.