Chris Rokos’s investment firm manages more money than Brevan Howard Asset Management for the first time as clients continue to quit billionaire Alan Howard’s hedge fund company. Rokos, who co-founded Brevan Howard and made $4 billion for the firm from 2004 to 2012, oversaw $8.2 billion at the end of March, according to a person with knowledge of the matter. Brevan Howard managed $8 billion on April 1, according to the firm’s website, a fall of more than 75 percent from its peak in 2013. Spokesmen for London-based Rokos Capital Management and Jersey-based Brevan Howard declined to comment.