Roseau, formerly Charlotte Town, town in southwestern Dominica, capital of the island nation, in the West Indies. It is situated at the mouth of the Roseau River in the Caribbean Sea. The town is a port and serves as Dominica's main commercial and transportation center. Tourism is also important to the community's economy. A Roman Catholic cathedral built in the 18th century and botanical gardens are here, and the twin waterfalls at Trafalgar, a popular tourist attraction, are nearby.