 In 2010, he sang Wotan in Richard Wagner's "Ring cycle" at the Los Angeles Opera, conducted by James Conlon, and the following year he sang in Wagner's "Die Walküre" at La Scala in Milan under Daniel Barenboim.Kowaljov has more than forty roles in his repertoire, and has notably performed as Padre Guardino in Verdi's "La forza del destino" at the Grand Théâtre de Genève, Banquo in Verdi's "Macbeth" with the Dutch National Opera, and Don Alfonso in Donizetti's "Lucrezia Borgia" with the San Francisco Opera.As a concert artist, he has performed at the Chorégies d'Orange Festival, and has performed with the Orchestra dell'Accademia Nazionale di Santa Cecilia, the Deutsches Symphonie-Orchester Berlin, the San Francisco Symphony, and the Chicago Symphony Orchestra.