The move means that if the Type-A free agents decline arbitration and sign other teams, the Brewers would be compensated with high draft choices.
First baseman Fielder, among baseball's top sluggers, publicly stated last year that 2011 would likely be his last with the club, which he helped lead to the National League Central title.
Fielder, 27, played in all 162 games while hitting .299 with 38 home runs and 120 RBI for the Brewers.
Relief pitcher Rodriguez, 29, nicknamed "K-Rod," was the bullpen set-up man for closer John Axford once Milwaukee obtained him in a trade-deadline deal with the New York Mets.
He went 4-0 with a 1.86 earned run average in 31 appearances for the Brewers after recording 23 saves as the Mets' closer last season.
Milwaukee also announced it has declined arbitration on Type-B free agent shortstop Yuniesky Betancourt, who hit .252 with 13 home runs and 68 RBI last season.