Head Coach Daryl Powell said: “After leaving Sheffield for Widnes Tangi lost his way a little last seaon, however Tangi Ropati is a proven player in the championship who adds pace and size to our already excellent backline options.
“I am confident he will be a huge plus for us as a team and will be a fans’ favourite in the coming seasons. We are almost done with our recruitment and I am delighted with the competition for places in all positions.”
Freer, 22, was York’s player of the year last season and is a past graduate of the Hull FC academy.
Powell added: “I am delighted to strengthen our front row options with the signing of Nathan from York. I was very impressed with him when we played against York last season and I believe he is a player that will thrive in our enviromnent by growing both as a player from a rugby perspective and as an athlete from a physical development point of view.
“After meeting him I was in no doubt that his desire to get better will see him become a very strong performer at our club.”