Primarily a right back, Fisher began his career in the English non-league with Farnborough Town before earning a big move to Celtic in 2013.
After making his debut in October 2013, he would go on to make 13 appearances in his first season at Parkhead, earning him a Scottish Championship medal.
After finding opportunities limited in his second season, he took the opportunity of a loan move to St. Johnstone last season making 23 appearances, scoring once in a 3-0 away victory at Hearts.
He made the move back to England to join the Millers for an undisclosed fee, signing a three-year deal at the AESSEAL New York Stadium.
He made his Rotherham debut as a substitute against Aston Villa before making his full debut three days later against Brighton and Hove Albion.