In the 2021 Census of Population conducted by Statistics Canada, Saint-Rosaire had a population of 932 living in 363 of its 395 total private dwellings, a change of 10.6% from its 2016 population of 843. With a land area of 109.53 km2 (42.29 sq mi), it had a population density of 8.5/km2 (22.0/sq mi) in 2021.[4]