In March 2006, Robertson signed with the Newark Bears of the independent Atlantic League. He pitched in two games for them, then on May 10 his contract was sold to the New York Mets. He spent the next couple months pitching for the Mets' minor league team, the Norfolk Tides, where he pitched in 11 games, finishing with a 1–6 record and a 7.68 ERA. After being released from the Mets, Robertson spent the rest of the season pitching for the Uni-President Lions of the Chinese Professional Baseball League.