After Miln's death in 1881 Le Rouzic became at the age of eighteen the caretaker of the , founded in 1882 by Robert Miln to present his brother James's collections to the public. After completing his military service in the
Navy, he returned to his position at the museum, where he led tours during the tourist season, an activity he continued until his death. From 1887 to 1895, he enriched the museum's collections by buying finds from farmers in their fields and he began to systematically record the megalithic sites in the surrounding area, but without undertaking any excavations because he did not have the necessary financial means. His activity was encouraged by , president of the and excavator of several Morbihan sites (Carnac,
Locmariaquer). In 1889, Closmadeuc entrusted him with the counting of the
menhirs of the Carnac alignments. The municipal council then added his name to the museum's name. From 1927 onwards Le Rouzic, being ill, undertook no major excavation projects but only restorations of monuments. In 1933, he was appointed correspondent and then member of the historical monuments commission for Morbihan. Between 1911 and 1938 he contributed to the registration and classification in the supplementary
inventory of historical monuments of around 120 dolmens and menhirs, and to the excavation and restoration of around 130 monuments. In 1935 he secured the return to Carnac of part of the collections of
Paul du Châtellier which had been bought by the
National Archaeological Museum, including objects from the excavations of , Arthur Martin and Louis Le Pontois. Many of his re-erections of the fallen stones in the Carnac alignments are now considered to have been wrongly placed. In 1937–1938, his restoration of the , at the request of the commission headed by
Abbé Breuil with whom he had an excellent relationship, caused a very significant controversy, first local and then national. In 1919, he became involved in politics, declaring himself "republican, democrat, secular and anticlerical" and contributed to the creation of the secular school and various secular social works in Carnac. He served as deputy mayor under his cousin Joseph Le Rouzic, and remained in that post until his death in 1939. == Publications ==