The 23 year old central defender joins the Millers on a 3 year deal.
He spent time with Man City but never made a first team appearance before joining Zulte Waregem, making 55 appearances and left this season.
The central defender has been capped for England up to Under-19 level while he made his debut for the Under-17s side aged just 14.
The defender flew out to Croatia on Tuesday to complete his medical and joined in with the Millers squad for their overseas training camp.