The defender has joined Steve Evans’s side on a free transfer after leaving Forest at the end of the 2014-15 season.
The former Sunderland player could make just eight appearances for the Reds in the Championship last season.
Collins scored one goal, had a pass accuracy of 75% and a shot accuracy of 50%, and won 17 headers and four tackles.
The former Stoke City man was on the books of Forest since 2012, but he did not have exactly a great time at the City Ground.
During the 2013-14 season, Collins scored one goal in 23 Championship matches. The 34-year-old had a pass accuracy of 80% and a shot accuracy of 33%, and won 102 headers, four dribbles and 21 tackles.
Following Collins’ move to Rotherham, Forest fans took to Twitter to have their say.
Below are the best comments:
Nottingham Forest fans:
Pleased that Collins has found a club. Solid pro who showed he could do a job in the championship when he came back in last season #nffc— Andy Hose (@ahosey31) July 3, 2015
Arrange these words into a well known phrase "Collins" "Quick" "Danny". You can't do it can you? #nffc— Gary N F F C ** (@ruddred) July 3, 2015
OH MY LORD Steve Evans just described Collins as quick! You've got the wrong player pal. #nffc— Adam (@OnlyOneOsborn) July 3, 2015
I would have played Collins ahead of Lascelles every game last season! #nffc— Andrew Cairns (@AndrewNewts) July 3, 2015
Glad Danny Collins has got a new club. He did OK when he came back in last season. #NFFC— Roman Filipowicz (@fritzromanov) July 3, 2015