Reluctant Bedfellow

Hi, I have acquired a new cockerel for my hens, but he will not roost with them. I Keep the chickens in an enclosed area 400m2 with elevated housing which they access via a rickerty ladder. The cockerel roosts on a pile of rocks. I managed to capture him on the first three nights and put him in with the hens. He has now cottoned on to this and chasing him round the pen by torchlight is not much fun. Whilst the weather was OK I left him alone but now the nights are getting colder I am worried he will not survive. Any suggestions gratefully recieved.