Roger Rosenblatt, former associate professor of English and director of expository writing, has accepted the position of literary editor of the New Republic, which was offered him by Martin H. Peretz, lecturer on Social Studies and the magazine's owner.

Peretz, who bought the magazine in April '74, said yesterday that he and Rosenblatt are "old friends," and that he thinks Rosenblatt is an "apt choice, because he's got taste, talent and wit."

Rosenblatt left Harvard in 1973 to become Director of Educational Programs for the National Endowment of the Humanities in Washington.

Wants to Teach

"I hope to go back to teaching someday because I miss it a lot, but at the moment I feel a desire and a need to write," he said yesterday.

Rosenblatt said he did not think he could write in a university atmosphere because he said he "needs more freedom than a university offers."

He had already turned down offers to consider two college presidencies.