It's probably for protection. It was originally designed to protect gamekeepers' heads.
http://www.telegraph.co.uk/news/uknews/8045026/History-of-the-Bowler-Hat.html
Brown touches the ball onto Gastón's toe which then kicks it in the direction he's running so although it looks as though Brown only brushes the ball he did momentarily change its direction. It was the follow-through that made it a foul, for me.
Having seen it again, I think Rose catches the back of the player's leg before he plays the ball, which is a foul. He's not running towards goal, however, so a yellow card would have been appropriate.