Roser is known internationally as a specialist for string puppetry. He is experimenting and developing in this field since 1951, based on his study with F. H. Bross, the genial German puppet maker. The goal of Rosers work is the unity of construction and performance or of technique and art. Technique must serve expression. Roser compares string puppets with music instruments which allow a great variety of precise and creative expression, at the same time requiring complete concentration on the performance.