Rivas signed as an un-drafted free agent by the Orioles in 2000 and spent the next seven years bouncing around in the organization (between Rookie and single-A). As a member of Gunma, Rivas played in only 9 games and batted .296 (8-for-27).
As for Pedroza, he was drafted by the Dodgers in 2005 and was then traded to the Rays in 2006. Pedroza took part in the Golden League the last two seasons (Calgary Vipers in 2009 and Orange County Flyers in 2010).
(UPDATE: the original Sanspo article I linked to mentioned a ペドラサ that played in the レッズ organization. A Sponichi article cleared things up with a mention of a ペドロザ that played for the レイズ organization.)