He has also appeared in a number of roles at Malmö Opera such as Demetrius in A Midsummer Nights Dream, Schaunard in La Boheme, Guglielmo in Cosí, the Crow in Stern's Snow Queen, Hans in Martinú’s Comedy on a Bridge and Morales in Carmen to name a few and My brother Don Juan at Unga på Operan/Royal Opera. He has also sung at Nordic Opera, Den Fynske Opera, Oslo Opera Festival and Vadstena Academy. Sebastian has collaborated with conductors such as Stefan Solyom, Wolfgang Wengeroth, B Tommy Andersson, Cathrine Winnes and Eva Ollikainen with, among others, the Swedish Radio Symphony Orchestra, the Norrköping Symphony Orchestra, the Helsingborg Symphony Orchestra and the Royal Philharmonic Orchestra. In 2018, Sebastian won the singing competition Havets Röst and has received a number of scholarships, including the Royal Academy of Music, Joel Berglund's Scholarship and Barbro Salén's scholarship.