We've done it from Spokane (GEG) so not that different from Seattle except you probably have more direct options.
The above advice is excellent. It's super annoying that you're almost compelled to overnight to get there, but that's how the flight schedules work out. A redeye was a possibility a couple of times, and Spokane friends we met in Roatan after we moved to Tennessee did that, but now that we're in TN it's a quick flight to IAH and same day to RTB.
Customs into Roatan can definitely be... challenging. They've always been very nice, very friendly, but it just takes SO long. We had one guy who thought he was being super clever, started my and my wife's "interview" with "So you were born in Hawaii" like he was going to catch us in a lie (?!?). We're both standing there, the second one of us heard him try it on the first one, he needs some fresh material! Good advice above to mentally prepare ahead of time.
Leaving RTB was long too, mostly due to the number of passengers. Which brings up a good point: If at all possible, try to fly in and out on a weekday. Saturdays especially are the default check-in/check-out day at AKR and other resorts. If you can get out of phase with everyone, you should have much lower congestion.
Be sure to give us a trip report when you return. We need updates on how various popular spots are changing.