House Democratic leaders expanded the Banking, Finance and Urban Affairs Committee by two seats yesterday to provide places for Thomas R. Carper (D-Del.) and Esteban Edward Torres (D-Calif.). Torres had lost a bid for a place on the panel in a close vote to conservative southerner Buddy Roemer (D-La.).

The expansion decision came after members of the California Democratic delegation voiced what one called "outrage" in a caucus yesterday that Roemer, a staunch supporter of President Reagan's budget, had been chosen for Banking by the Democratic Steering and Policy Committee over Torres, a freshman.

The steering and policy recommendations, made in closed session, are expected to be approved by the full House today.

In other action, the committee nominated six new Democrats to the Interior Committee, which oversees oil and gas leasing, parks and wilderness areas and Indian affairs: Alan B. Mollohan (W.Va.), Bill Patman (Tex.), Peter H. Kostmayer (Pa.), James McClure Clark (N.C.), James F. McNulty Jr. (Ariz.) and Richard H. Lehman (Calif.).

Members of the House GOP executive committee on committees also met in private to nominate Republicans to open slots on various committees.

Harold Rogers of Kentucky was chosen for the influential Appropriations Committee, which oversees all spending bills.

Carroll A. Campbell Jr. (S.C.) and William M. Thomas (Calif.) were selected for Ways and Means, which handles taxes and other financial issues.

The Republicans decided to hold open a seat on the Budget Committee for Phil Gramm, the Texas Democrat who was denied a Democratic seat on Budget and resigned from Congress to run again as a Republican.

Two other Republican vacancies on the committee would be filled by Connie Mack (Fla.), a freshman, and Texan Tom Loeffler.

Republicans chosen for the Energy and Commerce Committee, which oversees communications, clean air and other major legislation, included Jack Fields (Tex.), Michael G. Oxley (Ohio) and Howard C. Nielson (Utah).

The Banking Committee would get two new GOP members, John Hiler (Ind.) and Thomas J. Ridge (Pa.).

Republicans Daniel B. Crane (Ill.) and David O'B. Martin (N.Y.) and John R. Kasich (Ohio) were nominated for the Armed Services Committee, which oversees the Pentagon.

Virginia's new Republican member, Herbert H. Bateman, was chosen for assignments on Science and Technology and Merchant Marine and Fisheries.