And you know that how?
From Wikipedia(This was all published at the time that this happened):
In 2004, after years of public denial, Rose admitted to betting on baseball and on, but not against, the Reds.
Rose admitted in 2004 that he did bet on baseball. He thought that this would give him a chance to get back into baseball, but baseball only drove the knife deeper...If there was proof that Rose actually managed in an attempt to throw games in order to win bets, I would support his banishment...To date, I am unaware of any such proof...