That's The Hound of Rowan by Henry H. Neff.
Max McDaniels lives a quiet life in the suburbs of Chicago, until the day he stumbles upon a mysterious Celtic tapestry. Many strange people are interested in Max and his tapestry. His discovery leads him to Rowan Academy, a secret school where great things await him.
But dark things are waiting, too. When Max learns that priceless artworks and gifted children are disappearing, he finds himself in the crossfire of an ancient struggle between good and evil. To survive, he'll have to rely on a network of agents and mystics, the genius of his roommate, and the frightening power awakening within him.
Max and his roommate do indeed get an extremely spacious room since they're both "special". Each set of roommates does get a personalized dorm.
Likewise, there is a version of soccer/football (sorta?) that has a field that changes elevations as you play. Max is exceptionally good at it.
It's the first of 5:
- The Hound Of Rowan (2007)
- The Second Siege (2008)
- The Fiend And The Forge (2010)
- The Maelstrom (2012)
- The Red Winter (2014)
They seem very Harry Potter-ish at first, but quickly change in books 2-5.