I had thought the French re-editions of Lefebvre had dried up, but the brief text ‘Vers un romantisme révolutionnaire’, first published in 1957 in Nouvelle revue française, is just out in a new edition, with a ‘présentation’ by Rémi et Charlotte Hess. Rémi Hess was one of Lefebvre’s students and his biographer; Charlotte is his daughter and a specialist on German romanticism. This piece appeared around the time Lefebvre was splitting from the French Communist Party, and produced some debate – there was a book of discussions on it published in 1958 that included contributions by Tristan Tzara and Lucien Goldmann. Kurt Meyer’s 1973 book Henri Lefebvre: Ein Romantischer Revolutionär took this text as a designation for Lefebvre as a whole. The text was reprinted in Au-delà du structuralisme; and Lefebvre returned to this later as the longest of the preludes in An Introduction to Modernity had the title of ‘Towards a New Romanticism’. What’s interesting about the title of the reprinted piece is that it is romanticism that is the key term, modified by revolutionary, and not the reverse.
The publisher page has more details.