The ultimate guide for what to do & where to stay. Join the Community. Roatan is an island off the northern coast of Honduras and formed by the Bonacca Ridge, which is an underwater mountain range. Located in the western Caribbean, Roatan (ROA™) is approximately 40 miles long, 3 miles wide and has annual temperatures with highs of 89.6°F (32°C) and lows of 77°F (25°C). The Bonacca Ridge is responsible for the formation of several small islands and Keys in the surrounding areas including the Island of Utila and Guanaja. Roatan is home to the largest barrier reef in the northern hemisphere. There are three major coral reef formations in the waters around Roatan. Also, the Cayman trench is located just west of the island bringing with it rich nutrients which feed a variety of species and give way to one of the worlds riches marine ecosystems.