Dutch goalkeeper Roos has moved to the Millers on a season-long loan to provide competition for first-choice Adam Collin, while defender Rawson had spell on loan at the AESSEAL New York Stadium last season. He has signed a six-month loan deal.
Manager Steve Evans said: “Since the end of last season, I have made it clear that I would like to strengthen the Millers in the goalkeeping department.
“For me, there were only two options and I am delighted that we have been able to secure one of them on a season-long loan.
“I have watched Kelle on a number of occasions, as has our goalkeeper coach Andy Dibble, both of us have on every occasion left the match very impressed.
“I am absolutely delighted to have secured the services of young Faz. In a very short space of time towards the end of last season, he joined us as a boy and left us as to go back to Derby County as a man.”