QPR loanee Tom Carroll wants to "make it at Tottenham" but is prepared to consider all of his options at the end of the season.
Ilkay Gundogan has commited his future to Borussia Dortmund by signing a new contract.
The 29-year-old will be reunited with Millers manager Steve Evans, who was his boss at Crawley.
"A lot of hard work has gone into getting Matt Tubbs here, I am delighted," Evans told the club website.
"At the end of last season and before then I highlighted to my chairman he was my first-choice striker to be recruited, we have managed to get that done and accordingly I thank my chairman Tony Stewart."