will the water pump work off of a 2003 trooper work for my 2004 rodeo

If the Rodeo has the 3.5 liter engine, YES. Alex

you may want to change the timing belt and components while you're in there also, because the water pump is driven from the timing belt,and will work for either engine. The 3.2L and the 3.5L take the same parts,and both are Interference engines....