sorry for late reply.
yes, but I need to remind you that the Facebook Gameroom Native SDK(c++) is only open to some users which has been invited to Beta. So firstly, you should apply for the qualification.
After you clicked on “add product”, I think you should click “see more products". And you will find the “gameroom native” product there.
Facebook has not upgraded the Gameroom SDK for a long time. The last beta version was released on Aug 17th, 2017.