Los Rocas is in West
Bay - a couple miles west of the West End. I don't really see any reason to dive with Los Rocas if you're not staying there. Unless you like to ride the water taxi every day.
There's probably a dozen shops in the West End - more if you count resort affiliated shops like Splash or whoever is at Sueno now. Here's some to google in no order:
SunDivers
Native Sons
Coconut Tree Divers
Reef Gliders
West End Divers
Roatan Divers
etc.
My short list would be Coconut Tree (think DiveBVI but more fun) or Reef Gliders - I know the owners very slightly from our local dive scene b4 they moved to Roatan. But really all are good, established operations.
Some don't like CTD since their afternoon boats are DM training dives but frankly I did - I practically solo dive since I film so generally had my own DM shadow. Once when we were blown a little too west it was nice to have someone to talk to while waiting for the boat - which we could see picking everyone else up first.
Unless the plan is to save a few bucks by buying a 10/$350 pkg. - just about everyone has one - I think the suggestion to try other shops is a good one. In a week of diving we used 3-4. CTD, Barefoot and AKR plus I forget whose boat some of us dove with one night - since we dove around the island. It's virtually all boat diving so the rates are pretty reasonable compared to other locations.
Roscoe is right, it would help to know where you're staying to customize the list to shops nearby. End to end the actual West End is over a mile plus there's rentals past it in both directions.
All book the shark dive since that's done on the south side thru Wailuka - they own the concession. Most provide a ride, either included or for $10pp. on a shared van. Dolphin dives are at Anthony's Key - about a 10min drive east. Walk-ins are welcome you just pay a little more. Pre-book that too, we did one morning and had our own DM, boat and 3 dolphins for the hour.
you also might find this useful:
http://www.roatan.net/Roatan-West-End-Map.pdf
