It's hard to do in one day. Vern's Cat goes over one afternoon and comes back early the next morning. It's about a 4-5 hour sail.
The ferries through La Ceiba are also about a 4-5 hr. process - 2-5PM over - plus the obligatory hour through Roatan immigration if you fly in the same day - The next morning is a 6AM - Noon return - or there's an afternoon option also.
We did that going through Roatan on our way to a week on Utila - one flight vs. two through San Pedro saving about $500 r/t was the draw for us.
One of the divers who stayed at our resort was from your area - to fly he had a series of connections from Utila through SPS to MIA and back to Portland. IIRC it was going to take him something like 15 hrs on the return - with the time changes. I think he said it was 20 hrs. to Utila as the connections weren't as good.
There's a Continental flight through IAH that puts you on Roatan at Noon - assuming you can get there early enough to connect. After clearing Roatan immigraton (plan for an hour) a 10 min. cab ride followed by 3 hrs. on the ferries plus waiting time put us on Utila at 5PM. The ferries dock adjacent to each other in La Ceiba so the transfer is easy. $102 rt/pp. for all of it.
Subway Watersports offers a one day whaleshark snorkel from Roatan - no diving is allowed by law - trip. It's $700. They have a fast boat so go over in about an hour. Chances of seeing a whaleshark late Jan. are slim -the "season" runs from March-April typically.
3 years ago Seagrape also offered day trips to Barbareta, Utila etc. But it doesn't appear on their website now. I think that would be a rough ride on their open boats.
You might consider just going to Utila instead. If you ever bring the kids, they'd be bored on Utila much sooner. Roatan has more kid-based attractions, better beaches etc.
One of the absolute best dives I've ever done was Black Hills off Utila. It's a seamount that rises to 40' of the surface. On one dive - we saw 4-5 huge grouper, several dozen Barracuda, about 6 Oceanic Triggers in the 3-4' range and schools of Snapper etc. The grouper allowed me to get within about 5' while filming before slowly moving off. Add a couple of rays that flew by later.
If you want a quieter trip, stay at one of the AI's outside of town, Deep Blue, Laguna Beach or Utopia Village. We liked Deep Blue - a lot. Good food, great staff, all the rooms face the ocean 50' away. Lot's of Sand Flies so bring DEET.
Not being advanced, the shore diving off Laguna Beach is a little easier entry - off their beach vs. Deep Blue's where you have to be able to find a passage through the reef - the coral is pretty intense in that area. The 2 resorts are near each other. Both are on the opposite side of the mangrove lagoon channel so town access is limited - they'll take you over by boat several times a week or more.
I loved it there! Diving, eating, sleeping, hanging out on the hammock during surface intervals and before the night dive.....it's a great way to escape from civilization. In order to get to "town" you have to take a boat to get there, and you see the entire "town" within 1/2 hour.
