Roles included in her repertoire include: Elettra (Idomeneo]), Licenza (Il sogno di Scipione), Vitellia (La clemenza di Tito), Countess Almaviva (The Marriage of Figaro), Fiordiligi (Cosi fan tutte), Hélène (Les vêpres siciliennes), Eva (Die Meistersinger von Nürnberg), Elsa von Brabant (Lohengrin), Gutrune (Götterdämmerung), Rosalinda (Die Fledermaus), Agathe (Der Freischütz), Hanna Glawari in The Merry Widow, Diemut (Feuersnot), Leonore (Fidelio), Ariadne (Ariadne auf Naxos), Mimì (La bohème), Leonora (Il trovatore), Masha (Pique Dame), Governess (The Turn of the Screw), and Marguerite (Faust).
In the 2009/10 season in the program, Willis-Sørensen made her mainstage debut with the company as Masha in Pique Dame and covered Elsa in Lohengrin and the Governess in The Turn of the Screw.
In the 2010/11 season, she sang the role of Kate Pinkerton in Madama Butterfly and Fiordiligi in Così fan tutte as a part of the Houston Grand Opera Studio performances.
Later that season, she made her Santa Fe Opera debut as the First Lady in Mozart's The Magic Flute and performed excerpts from Arabella as a member of their Apprentice Program.
In the 2011/12 season, Willis-Sørensen made her Royal Opera House, Covent Garden, debut as Countess Almaviva in The Marriage of Figaro under music director Antonio Pappano.
She was to have made her role debut as Alcina at the Semperoper Dresden,[1] and sing Contessa Almaviva in The Marriage of Figaro at the Grand Théâtre de Bordeaux,[1] but these engagements were cancelled due to the COVID-19 outbreak.
[16] Willis-Sørensen started the 2021/22 season with a gala at the San Francisco Opera which featured mezzo-soprano Jamie Barton and Music Director Eun Sun Kim.
[25] In November 2022, Willis-Sørensen made her role debut as Elisabeth in Verdi's Don Carlos at Lyric Opera of Chicago[26] followed by a return to the Wiener Staatsoper to perform Die Fledermaus.