Rosen was a student of Leo Strauss at the University of Chicago, where he defended his dissertation on Spinoza in 1955. He was also a student of Alexandre Kojève. He did his postdoctoral work at the American School of Classical Studies in Athens, and became Evan Pugh Professor of philosophy at Penn State University and then Borden Parker Bowne Professor of Philosophy at Boston University. He has held the Companys Lectureship at the University of Barcelona, the Cardinal Mercier Lectureship at University of Louvain, the Priestley Lectureship at the University of Toronto, and the Gilson Lectureship at the Institut Catholique in Paris.

Rosen's first two books, a study of Plato's Symposium and Nihilism: A Philosophical Essay, represent his abiding concerns. On the one hand he continuously returned to the roots of the philosophical tradition, in particular to Plato, and on the other he thought through current critiques in reason and philosophy by confronting the most powerful representatives of contemporary thought. The most notable feature of this engagement was the passionate desire to see as much as possible that is of value in other thinkers before making his criticism. Thus in Nihilism he confronts the two main strands of contemporary philosophy, the analytical and continental movements, at their peaks in the works of Heidegger and Wittgenstein.

Like his close contemporary Richard Rorty, Rosen criticized both analytic philosophy and continental or postmodern thought. Despite this strong similarity, the alternatives proposed by these two thinkers are very different. Rosen took the philosophy of Jacques Derrida more seriously, in particular his interpretation of Plato's Phaedrus. Rorty argued that from postmodernism can be salvaged an edifying destruction that "keeps the conversation going." Rosen countered in Hermeneutics as Politics that this view of traditional philosophy is unduly pessimistic and even reminiscent of the Nietzschean sense of "reactive."

One of the central themes of Rosen's work is the claim that the extraordinary discourses of philosophy have no other basis than the intelligent understanding of the features of ordinary life or human existence. This theme was given an in depth treatment in his recent work, The Elusiveness of the Ordinary.

Rosen has educated several generations of students in philosophy. It is a mark of the non-dogmatic nature of his teaching that several of his students who have since become eminent themselves have adopted a wide variety of philosophical positions and styles.