The Belgian international was signed by David Moyes from Olympiacos last summer, and although he was happy playing for the Scot, he feels that the former Wigan Athletic boss can get the best out of him.
"The major change for me is the language change because I speak Spanish," PA Sport quotes the 26-year-old as saying. "For me it is better, although I was very happy playing under David Moyes because he is a good manager, but Roberto is different because the Spanish style of playing football is different.
"The Spanish style of football is my type of football and with Roberto it is very different. Every day I have spoken with him and it's helped my confidence.
"It's better because under David Moyes I was not as free but now I am on the line more under Roberto - it's different but that's what Roberto wants me to do. I feel I am more consistent now. I play better and better. The first game I was not so good and felt tired but now my body is excellent and everything is OK."
Mirallas scored his second goal of the season in a 2-1 win over Hull City on Saturday.