We just got back from Honduras on Sunday.
The ferry runs daily from LaCeiba to Roatan. It leaves La Ceiba at 9:30 and arrives in Roatan at about 11:00. There is supposed to be a new high-speed ferry that takes less time, but when we got there, there was just "the ferry" -no choices. IIRC, it was about $20 US per person.
You want to arrive about 1/2 hour early at least - especially if you are checking baggage. The baggage claim process at the Roatan end was painfully disorganized - I had to keep telling myself, this IS Honduras.
Also if you're at all inclined to be seasick I'd consider flying instead. (I think a ticket on SOSA from La Ceiba is about $75 - check their website). Even on a calm day the surging just about did me in, and I don't usually get seasick. They walk thru the cabin passing out barf bags as soon as they get going. Take one!
Hope that's helpful.