Roca has become United's third signing of the summer, joining the Whites from Bayern Munich for a fee in the region of £10m.
The 25-year-old has signed a four-year deal at Leeds and says he will combine tough tackling with passing skills in the Whites midfield.
“My favourite position is a midfielder," said Roca to LUTV, asked what sort of player he was.
"I like to play with the ball, to be strong in defence and always helping the team.
“The fans can expect me to give my everything.
"I am a player who loves playing with the ball, but I am hard as well in defensive duels."
Roca follows in 21-year-old USA international midfielder Brenden Aaronson and 24-year-old Denmark international right back Rasmus Kristensen through the entrance door at Elland Road this summer.
Leeds only secured their Premier League status on the final day of the season last term but the Whites have already parted with around £45m to sign Aaronson, Kristensen and Roca.
Aaronson and Kristensen have been recruited as part of a double swoop on Austrian champions RB Salzburg.
Pressed on the challenge for Leeds next season, Roca said: "I have to know my new team mates, my colleagues, but I hope Leeds is a team that wants to go in the best position that we can.
"We will do our best, not only for ourselves but for our fans as well."