Rolls are seaweed, rice, a few veggies, and possibly a little strip of meat. Most buffets can handle that very well for the average rolls. Imitation crab, basic tuna, basic salmon, and and tempura shrimp are all simple enough to do to make a good roll.
Sushi rolls are cheap and easy to make. Most places charge way too much for them. At least for the cheaper style rolls. There are more expensive rolls that can be made from more expensive ingredients, but again the price on those go up proportionally.
Anyone claiming that rolls made at a high end restaurant of the same type of roll is better than a fresh made roll from somewhere else just has
post purchase bias in regards to inflating the worth of the pricier sushi roll just because it was more expensive in the first place.
Sashimi is a bit different than sushi rolls, and you don't see buffet places typically do pure sashimi platters for that reason.
I go to high end japanese sushi restaurant for good sashimi and rolls I can't get at other places when the mood strikes me. I don't go to a high end japanese restaurant for a California roll that costs $15 when I can get the same thing from a many other places for much cheaper.