Roos has impressed during a two-month stay with the Conference Premier side, and chief executive Ian Neale has revealed that the 21-year-old has been in demand since his arrival at the club.
Neale is quoted by BBC Sport as saying: "He really has been in demand. Just two months ago when he signed for us, not many English clubs knew much about him.
"Kelle will be missed at the club, despite him only being with us for a very short time. He has every chance of having a brilliant career."
Roos, who started his career at PSV Eindhoven, went on trial with Liverpool for a week before signing a deal with the Rams.