For future reference, there is alot of information on Roatan in the Central America section. My take on the weather is this...April-May are generally fairly windy and can have rough seas. Late March to Early June are the peak of thimble jelly season in the Caribbean, but my experiences in March 1999 and May 3-10, 2003 were not bad at all. If you go in the spring you miss hurricane season, if you go in the winter, it is rainy season. Rainy season in Roatan as I understand it runs from about October to the end of January. So the only real time you should expect calm clear water is June - October, which just happens to be hurricane season. Being as far south as they are, Roatan doesn't see a large number of hurricanes, but they did get a direct hit from Mitch in October 98 and have seen rough weather from two others since than that ended up heading into Belize instead. My advice if you want the best conditions is to book early in the summer (might be hot, but they tend to get more tropical weather action late in the hurricane season) and get trip cancellation/interruption insurance that covers weather related problems. That is also considered low season, so you should get some good prices also.
AggieDiver