The Germany defender has followed Mohamed Salah to the Premier League, and their former team-mate is concerned about their sales
Kevin Strootman hopes Antonio Rudiger's move to Chelsea will be Roma's "last goodbye" of a difficult transfer window.
The Premier League champions completed the signing of the Germany international on Sunday in a deal that could cost them up to €39million.
Roma have already sold Mohamed Salah to Liverpool and Leandro Paredes to Zenit in the close-season, with Francesco Totti retiring, while there has been speculation over the futures of Radja Nainggolan and Kostas Manolas.