Yes, you can drink the water in Roatan at restaurants. And eat the ice! Drinking water on Roatan is distributed by a water purification company that all businesses and residences use. Hotels &AirBNBs will provide access to drinking water. The water is completely distilled, meaning there are no trace minerals, so if you want to ensure you are getting some nutrients with your water we recommend bringing electrolyte packets.
While not potable, most water that comes from the bathroom sink is fine to brush your teeth with, but you can use the purified water if you do not want to take your chances. Sink water is also fine to cook boiled foods in and wash fruits & vegetables in, though produce should be completely dry before consuming raw.