Rotherham are unlikely to make any more signings before the end of the month, according to manager Steve Evans.
Derby captain Richard Keogh has agreed a new three-year contract with the Sky Bet Championship outfit.
The 25-year-old Hungary international joined Wanderers in the summer of 2007, moving from boyhood club Vasas SC.
Following a single appearance during a loan spell with Crewe two years later, Bogdan made his Bolton debut in the August 2010 League Cup trip to Southampton and went on to play nine games in all competitions that season.
At the turn of this year an injury to Jussi Jaaskelainen offered him another first-team chance and Bogdan went on to dislodge the long-serving veteran as Bolton's No.1, a position he retained this season despite Andy Lonergan's arrival from Leeds.
"I'm delighted with the extension," he told the club's official website. "I think it's always a good feeling when the club wants to extend.
"I hope it's a good message for everyone and proves that I see my future here and that I am enjoying playing for the manager. I want to get back to the Premier League as quickly as possible and I see this as a big step."