DH and I are both Southerners now living in Yorkshire.
My roast consists of 1 meat, mixed roast veg (carrots, parsnip, sweet potato, pepper, red onion and butternut squash), roast potatoes, stuffing or yorkshire pud and gravy.
MIL's roast consists of - 1 meat, every vegetable (literally) she can find in the supermarket either roasted, mashed or boiled, roast potatoes, cauliflower cheese, bread sauce, gravy, stuffing, and yorkshire pud. I can never finish it!
My Mum's roast - 1 meat, a few select seasonal veg, roast potatoes, stuffing or yorkshire pud, gravy.
My point being - there is a traditional idea of what a roast "should" be but everyone does it a little different. I wouldn't do mash and roast potatoes, but I do do 2 different types of potato!