This fall's plethora of one- and two-character "plays" continues erratically.

Dore Schary's "FDR" with Robert Vaughn as the second President Roosevelt, will cut short its run at the National with Sunday's 2 o'clock matinee. It was supposed to have continued through Dec. 4, but now will conclude its tour instead of venturing to New York in January. Those who already have seats for next week should contact the box office.

Phillip Hayes Dean's "Paul Roberson," starring James Earl Jones, has a new director, Lloyd Richards. He replaces Charles Nelson Reilly, who did the original staging. It will play the National Dec. 5 through 31 under the banner of Don Gregory, who presented not only "FDR" but two winners in one-character works: Henry Fonda in "Clarence Darrow" and Julie Harris as Emily Dickinson in "The Belle of Amherst."

Tuesday night Randall Duk Kim opens his one-man study of Walt Whitman, "Walt," which the Hawaiian actor adapted and which is directed by Annie Occhiogrosso. The run in the Chautauqua Tent on the Kennedy Center Roof Terrace will be through Dec. 10. On noon Wednesday, the day after the opening, Kim and Occhiogrosso will discuss their work at the weekly Performing Arts Symposium in the AFI Theater, Theresa Keane will be the moderator.

"Bernhardt," by Sarah Ban Breathnach, is a one-character piece about the French acting star. The place is the new ASTA Theater, 507 8th St. SE. The opening is Wednesday night, and it will play Wednessay through Sunday evenings at 8 through Dec. 18. The actress will be Madeleine Potter.

It's a characteristically large cast for Shakespeare's "Two Gentlemen of Verona," which starts previews Wednesday at the Folger Theater Group's intimate home under the direction of Louis Scheeder. New to the company will be Franchelle Stewart Dorn, Mikel Lambert and Michael Tolaydo. David Gropman's setting is his first such Floger assignment, and the score will be by William Penn, the theater's resident composer. An album of his work for Shakespearean plays will be released shortly at the Folger.

With Harlequin's "Anything Goes" in its final two weeks, the Rockville dinner theater's next show will be "She Loves Me" by Bock and Harnick, who created "Fiddler on the Roof." The setting is Vienna at Christmas time and the score has been a cult record favorite, starring Barbara Cook, ever since its disappointing New York run. Director Dallet Norris's cast will include Tricia Pearce, John Combs, Rick Ellis, Michele Somers and Buddy Piccolino. The run begins Dec. 8.

Les Bateleurs, the French-language acting group of Georgetown University, will present a staged reading of "Par dela les Marronniers" ("Beyond the Chestnut Trees") by a young Paris writer, Jean-Michel Ribes.It written in homage to the Dada movement, which was one of the major topics in Tom Stoppard's "Travesties." Performances will be Dec. 2 and 3 at 8 p.m. in Stage Three, Poulton Hall, 37th and P Streets NW, under the direction of the French department's Roger Bensky.

Friday opens the Hartke Theater's "The Corn Is Green," the Emlyn Williams drama about a Welsh school-teacher that revived the career of Ethel Barrymore. Robert T. Meyer, Catholic University's Professor of Celtic, is coaching the Welsh accents. . . . Ted Shine's "Morning, Noon and Night" will begin two weekends of performances Dec. 1 for the University of D.C. Environment Theater, 916 G St. NW., with the communicative arts department chairman Robert Edward West as director.