"He had never seen so many things he liked to eat on one table: roast beef, roast chicken, prok chops and lamb chops, sausages, bacon and steak, boiled potatoes, roast potatoes, fries, Yorkshire pudding, peas, carrots, gravy, ketchup, and, for some strange reason, peppermint humbugs" (Sorcerer's Stone 123).
We're back again at the glory of the first Hogwarts Feast. Unfortunately, I could not find a recipe for vegetarian roast chicken. There are, however, lots and lots of vegetarian chicken substitutes commercially available. In case you were wondering:
Morningstar is always my go-to for meat substitutes, mostly because it was the most readily available brand when I went vegetarian eleven years ago. They don't have a very "roasted" tasting chicken substitute, but they do have lots of chicken-y options.
Boca is the other most well-known brand of vegetarian-friendly meat products. Their products are very similar to Morningstar's.
Lightlife is another fantastic option, and their products are often no-carb, which is nice for those people who care about that sort of thing. They also have more of a cutlet-style "chicken" available, versus the battered-style "chicken" of Morningstar and Boca.
Gardein is another product line (that I think is a newer brand) that offers many varieties of frozen (and fresh) vegetarian and vegan products. Their "chicken" options are pre-seasoned to create things like "chicken scallopini" or "mandarin chicken." I've only ever used their "Beef tips," but they worked really well.
Quorn is a British-based product that I only recently started seeing for sale in American health-food stores. The only product of theirs that I've tried outside of the UK is their "Turkey roast," and it was pretty delicious; not as great as a Tofurkey, but still pretty great.
Seitan is another great option, but I can't find websites for the brands I buy. Just go to your local Whole Foods and check in the refrigerated tofu section.
So there you go! Not quite the greasy, juicy, gravy-covered joy Harry expected upon seeing roast chicken on the Gryffindor table, but still some pretty good options for us vegetarians!