RR doesn't have much trade value. He has value to the Celts if he gets a new contract, but I think the issue is how much RR would demand and how much would DA be willing to settle on. All of that, however, is predicated on the assumption that RR has a serious interest in staying with the Celts.
If DA does trade him, I doubt he could do better than a late 1st and some cap space. Any team that trades for him does so as a short-term rental. DA is a shrewd trader, but he is not a magician.