Effective new Broadway roles for Roy Dotrice, Anne Bancroft

Kingdoms Historical drama by Edward Sheehan. Starring Roy Dotrice, Armand Assante, Maria Tucci. Directed by Paul Giovanni.

Temporal power strives with ecclesiastic authority in the ambitious new historic drama at the Cort Theater. In ''Kingdoms,'' his first produced play, journalist-author Edward Sheehan has tackled nothing less than the secular-religious conflict between Napoleon and Pope Pius VII. Covering the period from 1804 to 1814, the play is necessarily episodic and at times somewhat difficult to follow. But Mr. Sheehan's concentration on the power struggle itself - plus fine performances by Roy Dotrice, Armand Assante, and Maria Tucci - result in a stage work that achieves both distinction and theatrical effect as it examines the shifting personal relationships in a historic confrontation.

The sweeping overview begins in Paris with the negotiations between Napoleon and Pius over such matters as church-state rights, the Emperor's self-coronation , his marriage to Josephine (without witnesses), and the future of the papal states. After Napoleon had violated various provisions of the concordat, the French occupied Rome in 1808. Napoleon was excommunicated in 1809, whereupon Pius was arrested and held - first in Italy and later at Fontainebleau - until 1815.

Considering the weight and complexities of the issues involved, it is not surprising that ''Kingdoms'' must be a highly compressed and probably oversimplified version of what happened. As Mr. Sheehan notes in the Playbill, ''most of the dialogue is invented, many of the historical events are telescoped in time, and numerous other liberties have been taken for dramatic convenience.''

Fortunately for its viability as a stage piece, the ''Kingdoms'' dialogue is literate, gracefully ironic, and at times passionately urgent. As is usually the case with plays about tyranny and its victims, the victim is dealt most of the best cards. As a result, Mr. Assante must for much of the time posture and dominate and bully those about him. Roy Dotrice's pope, on the other hand, suffers with grace, patience, and courage the indignities and cruel deprivations inflicted on him by an egomaniacal despot as he seeks to get the excommunication revoked. Miss Tucci, that most womanly of actresses, plays the eventually discarded Josephine with strength as well as appealing femininity.

Paul Giovanni, who has a flair for this kind of heroic theater, has staged a performance of considerable power and an authentic feeling for courtly and military ceremony as well as for drama in high places. The requisite histrionic flourish for ''Kingdoms'' is admirably provided by a cast that includes Thomas Barbour as the resolute Cardinal Consalvi, George Morfogen as a despicable Cardinal Fesch (Napoleon's uncle), and Michael Tolaydo as General Radet, the ''toy soldier'' placed in charge of Rome, whose arrest of Pius may or may not have been authorized by the emperor.

''Kingdoms'' has been austerely but imaginatively designed by David Hays. Heroic-size paintings of a Napoleonic victory and of his army's disastrous defeat at the Berezina River on the retreat from Moscow provide a visual introduction to each of the two acts. A few well chosen pieces of period furniture and an arrangement of panels create the atmosphere for the succession of scenes played out on the raked, dark-blue-carpeted stage. The rich costumes are by Patricia Zipprodt, and the distinguished production has been artfuly lighted by Paul Gallo.