The England international is in talks over a new Manchester United contract, and the Spain star is looking forward to setting up plenty of goals for his new teammate.
Rooney is understood to be in talks over a big-money contract that would keep him at the club for the long term, after Chelsea had an approach for the striker rejected earlier in January.
The England international is back in training following an injury, and Mata is eagerly anticipating the chance to "connect" with the striker.
"For me he is one of the best players in the history of this country," Mata told reporters at his unveiling. "He's an unbelievable player - he can score and he can assist - and I will try to connect with him as much as I can. I think that's my best way of playing - trying to find the gaps in defenses, to be in the positions I need to be in to assist the strikers."
Robin van Persie and Marouane Fellaini have also returned to training after injury as United attempts to climb the Premier League table in the second half of the season.