Hitchcock, 20, came through the ranks at Blackburn and after moving to QPR in March he was a regular scorer for their development side.
He enjoyed a spell on loan at Plymouth earlier this season, making 10 appearances.
O'Toole, 24, began his career with Watford and spent time at Sheffield United before moving to Colchester in September 2009. He has made 71 appearances for the U's, with 11 coming this season.
"I know John-Joe pretty well from my own time at Colchester," Rovers manager John Ward told the club's official website. "He is a really strong midfield player and he has a little bit of experience, having played in the Championship with Watford.
On Hitchcock, Ward said: "It's a big test for him but he's a hard working young player who has a goal in him and we will have to work hard to play to his strengths."