Washington ? As a legal adviser to President Reagan, Supreme Court nominee John G. Roberts Jr. joined a scathing denunciation of abortion-clinic bombers and urged Reagan to stay out of an effort to post tributes to God in Kentucky schools.

Roberts’ advice, in documents Knight Ridder obtained before their public release later this month, might help him counter critics who portray him as a doctrinaire conservative. Abortion-rights groups and organizations that advocate a clear separation between church and state oppose his nomination.

Both sides in the nomination debate are scouring court briefs, legal memos and other documents for anything that can help make the case for or against Roberts’ ascension to the nation’s highest court. The documents that Knight Ridder obtained were leaked by an administration official who wanted to show the nominee as a servant of the law, not of conservative ideology.

In another development that could confound Roberts’ liberal critics, the Los Angeles Times has reported that he worked behind the scenes, without charge, for gay rights activists in a 1996 case that led to a Supreme Court ruling protecting homosexuals from discrimination. Roberts, who was then in private practice, was asked to join the case by a colleague at his Washington law firm.