He isn't Thiago. Rafinha is a hard worker, but he won't become anything more than a rotation option, but problem with even that is that he's so injury prone. Roberto a better midfielder. Rafinha is not the fastest player, not very creative or got size on him.
Even if he stays, he doesn't have a long-term future at the club IMO and will more likely get surpassed by someone like Alena in a season or two.
If we can manage to get 30m for him, then I'd absolutely sell. When it comes to Arda and Gomes then I'd obviously sell them too without a shred of doubt.
If we can get close to what we paid for Gomes then sell him. As for Arda then try to sell him to the highest bidder.