Roberts made four appearances for Norwich City during the first half of this season.
Boro head coach Jonathan Woodgate said on the club website: "It's great Patrick has signed up.
"He is an exciting player, he wants to play games, and he has the bit between his teeth.
"He fits the mould of what we are looking at. He is young and hungry, and wants to do well.
"I am absolutely delighted to have a player of Patrick's calibre at this football club."