“Shane is an experienced player with a lot of games under his belt, including a Grand Final win,” Harlequins coach Rob Powell said.
“He is also a decent defender and will provide good strike on an edge.
“Antonio has been playing some of the best football of his career this season for Newcastle, the sort of form that saw him play for Australia a few years ago.
“He is a big explosive prop and will add a lot to our pack.”
Rodney has played 125 times in the NRL for Penrith and Manly while Kaufusi has also played Tests for Tonga and Australia.