why the fuck are you limiting it to 4 veg? Roast anything should feature, as a minimum, the following accompaniments:
Roast potatoes
Roast pumpkin
Roast carrot
Roast sweet potato or parsnip (if not both)
Roast onion (and/or leak)
Boiled/steamed cauliflower
Boiled/steamed broccoli
Boiled/steamed zucchini
Boiled/steamed peas and/or beans
Personally, I’d throw in some corn (on the cob or otherwise) as well, and maybe some sprouts too.