Maybe not every Sunday, but certainly in the colder months its most Sundays (for us anyway). It doesn't get boring because its not always roast beef....in this house roast pork/ham, lamb, chicken, venison, duck are also on the menu. And there are so many different cuts (which require cooking in different ways) that there's quite a variation really. Then you can add in things like roasting the joint on the BBQ or rotisserie instead of in the oven, rubbing the meat with different herbs and spices, plus if you add in the sauces: mint sauce with lamb and mutton, apple sauce with pork, gravy, it creates even more variations.
The veg tend to be seasonal - a combination of whatever we have ready from the garden/allotment, or the local market if we want something a bit different. Sometimes we'll also have stuffing (sage & onion is my favourite) or yorkshire puddings - but not every week.
The only thing that pretty much stays the same from week to week are the roasties. But I happen to love roast potatoes so its no hardship having them regularly....they've got to be cooked in goose/duck fat, dripping or lard though....never oil! Nice and crunchy on the outside and soft and fluffy on the inside.
Yes I'd totally agree....Christmas dinner is basically a Sunday roast but with lots (and lots!) of added extras. Except for us it has to be turkey or duck - it just wouldn't be right with anything else.
And the best thing? If you're used to cooking a Sunday Roast regularly, then Christmas dinner is a doodle