Olsson told the club's official website: "I'm very happy, it feels good to play in the Premier League again, to be with a Premier League club, so yes I'm excited.
"My dream has always been to be in the Premier League but Rovers went down into the Championship, which was a good lesson for me. I learned a lot of things.
"But I'm at a new club right now, so I'm looking forward to meeting the players and enjoying my time here."
Olsson made 143 appearances for Rovers in his seven years at the club.