We used to do hunks of beef and lamb regularly, but prices have gone through the roof.
In period, they mostly boiled them, as it was easier and suited the older beasts which were more available. You throw some pot herbs in the water, which becomes the stock for the next day. We still do that at Festival.
The other way that bulk meat was cooked was on a spit, and we do that at Festival too, for pork and geese and chickens.
Actual roasts in an oven was rare, as they just didn’t have the oven space. I do however like to do whole roasts, and to send them out whole to tables to carve themselves. In many ways, that’s a terrible idea: you need big ovens (or Aldi smoker ovens!), and you must provide carving boards and sharp knives to every table. Physically shipping them out to tables is non-trivial.
The alternative, not nearly so fun, is to cook them beforehand, slice them in slow time, and freeze them on flat baking trays for a quick re-heat on the night. Makes me shudder to think it, but my more practical feast stewards tend to prefer that.
If you are doing a roast, you should provide a sauce. Preferably two, but that’s heroic.
My go-to sauce for beef is Corans sauce. Basically you buy a box of currants (the mini sultanas, not the fruit) and a cask of cheap red wine. Bung them in an electric crockpot in the corner, with a couple of stock cubes, and forget till serving time. Consistently delicious, and some people will ask to take the remainder home. (There are fancier versions of the recipe, but the basic one works well.)
Bonus points if you put out some mustard as well! (My cheat for lots of dishes is a runny sauce of dijon mustard mixed with white wine vinegar.)
At other times lamb has been cheap. Right now, we mostly do pork if we want to have a roast.
My usual sauce for pork is Appulmoy, where you thicken the stewed apples with ground almonds.
Alys does a really good green sauce, of seasonal herbs from our garden, with some apple, blended with breadcrumbs and lifted with a little vinegar.