Depends on the meat.
Beef it ours be Yorkshire puddings, cauliflower or broccoli cheese, roast rot veg - beetroot, carrots, celeriac and parsnips. Baby leeks with cheese, mashed swede with mace.
Lamb might be stir fried green beans, pepper, baby corn and onion, in mint butter. Hassleeback potatoes or dauphinois. Fennel. Roasted and mustard glazed baby turnips. Roasted half elephant garlic. Usually a herb stuffing.
Pork maybe stuffed apple cups, crackling obviously, Brussels sprouts stir fried with pancetta, red cabbage with apple and star anise, celeriac purée. Carrots roasted with paprika.
With a salmon, I’d do asparagus if in season, peas with baby silver onions, sauté courgettes, roasted lettuce or chicory.