Rodriguez was elected to the U.S. House of Representatives in 1987 to fill the vacancy caused by the death of Democratic U.S. Representative Frank Tejeda. Rodriguaz won the following two elections, but lost his re-election bid in 2004 to fellow Democrat Henry Cuellar of Laredo, Texas. He won back his seat in Congress in the 2006 election when he unseated the Republican Henry Bonilla, also of San Antonio.
Rodriguez is one of three U.S. House Democrats from Texas who were unseated in the general election held on November 2, 2010. He lost to Republican Francisco Canseco, a native of Laredo who now resides in San Antonio. Rodriguez has announced that he will challenge Canseco in the 2012 election.