R. Opisso was the graphic chronicler of an era. Self-taught, as he attended La Llotja, the Barcelona School of Fine Arts, for just one day, he soon joined the Modernista circles, taking part in their discussions and coming into contact with their leading members. He worked as an apprentice in the workshop of the architect A. Gaudí, a friend of his father's, making drawings and taking care of the photographic archive of the mouldings of the sculptures.

In 1898 he started to publish in the Modernista magazine Luz. Later on, he became a member of the Cercle de Sant Lluc (Circle of Saint Luke) and held his first exhibition at Sala Parés (Petritxol, 5) together with other members of the Circle. Between 1906 and 1912 he lived in Paris, where he was heavily influenced by the French draughtsmen of the period and where he contributed to many graphic magazines, depicting the city's bohemian atmosphere.

On returning to Barcelona he actively participated in the artistic and literary discussions at the Quatre Gats café (Montsió, 3 bis).

He regularly contributed to magazines such as Cu-Cut!, La Campana de Gràcia and L'Esquella de la Torratxa and became known, especially from 1910 onwards, for his so-called "multituds" ("crowds"), drawings with a large number of human figures and a very urban atmosphere about them. He also illustrated children's books.

In addition to this, he painted. His Carretó de cafè amb llet (Milk Coffee Cart, early 20th century; MNAC collection) is a good example.

There is a legend according to which on 14 April 1931, after the Esquerra Republicana party had won the elections, Lluís Companys was walking along the street towards Plaça de Sant Jaume with the intention of proclaiming the Republic, inviting the friends he met on the way to accompany him. One of the friends he came across was R. Opisso who, thinking it was a practical joke, went with him as far as Plaça de Sant Jaume, where Companys actually did what he said he was going to do; proclaim the Catalan Republic.