Make sure that however many types of vegetables you plan to do, that there is at least one type that each person will eat. But don't feel you need loads of different types - one or 2 favourites would be sufficient, 3 at the most.
Sometimes, especially when you might have limited oven space, you might find doing a pot of mashed potato to supplement the roasties can be useful.
Someone already mentioned that you should take out the meat an hour before carving so, as long as you have them already prepped at that stage, you can cook roasties and roast veg dishes etc in the oven once the meat is out without any pressure. Put the meat on the carving dish, cover in a layer of tinfoil, and then put a couple of bathtowels folded up over that to keep the heat in and it will still be steaming hot after an hour. (Check the carving dish periodically to drain off any juices coming out, so you can add those to the gravy!!).
I usually prep my veggies and potatoes the day before and mostly store soaking in water in pots or plastic tubs (potatoes, carrots, sprouts) but some things are put into airtight plastic tubs with no water (parsnips, onions, peppers, mushrooms, courgettes). I usually have them already chopped, but sometimes not (e.g. I often peel but don't chop garlic ahead of time).
Things that will go straight into the oven without any boiling, I may store them in a Ziploc bag with any oil and seasoning on them already (e.g. baby potatoes with olive oil, salt, pepper, chopped rosemary and garlic granules). Or I may have the herbs chopped and put them with the rest of their seasonings in a smaller airtight plastic tub (e.g. oil, salt, pepper, juice of a clementine, thyme, marjoram and garlic - for pouring over roasted root veg including carrots after their initial steaming for 15 minutes).
It might be useful to buy tin foil roasting dishes if your oven space is tight and you don't have a lot of roasting dishes, as you may be washing and reusing them otherwise.
2 easy veg that require minimal prep as additional sides are:
Frozen petits pois peas - remove from freezer and tip into a bowl to allow to thaw in the room for the morning, shortly before serving drain off defrosting water and cover with boiling water in the bowl, just cooks them perfectly, drain off water to serve.
Baby spinach - put the leaves into a metal colander or large metal sieve - wash thoroughly and let drain. Immediately before serving, pour an entire kettle of boiling water around and through the colander/sieve and let it drain in to the sink. I tend to then press the spinach to remove some excess water. Spinach is now perfectly wilted.
Think about your dishes for cooking and serving.
Will you want the same pot for 3 different things? If so, will that be at 3 different times (so having someone on washup duty will get around that) or are 2 things supposed to cook at the same time (uh oh - need an extra pot!)?
How many things will be passed around the table? Do you have enough bowls, serving spoons, jugs for gravy etc? Is it better to have 2 smaller bowls of 1 thing that everyone will want (1 for each end of the table) but 1 bowl of a less favourite item might be ok to pass all the way around?
Should you have 2 or 3 jugs for gravy? Can a couple of ordinary milk jugs be used as well as gravy boats, and washed before being used later for tea/coffee etc?
I always recommend when doing a big meal to have the kitchen sink full of hot sudsy water as much as possible, to be able to throw in the various things as you finish with them (or in the odd spare quiet patches) and get them washed and out of the way. Someone might dry up as you go, or come and clear occasionally. But getting the washing done can be a HUGE benefit to keeping surfaces clear to work on and being able to get the various tools/pots/utensils etc back to use again for something else.
Just make sure that, if someone kindly volunteers to be a "washer-upper" for you, that YOU put the things to be washed beside the sink in the designated washup area, and they don't just TAKE things from the work surfaces that look finished with (because you might not be finished with that particular knife or spoon yet).
Having plenty of clean and dry tea towels, hand towels, cloths for wiping the worktop and spills (and a roll of kitchen towel for this too), and spare oven gloves and aprons, can be helpful if you have people likely to offer to help you.
BUT be clear about WHO is doing WHAT!!
No one else just wanders in and opens the oven door or chops the carrots into slices when you wanted batons or covers the part-baked rolls in poppyseeds when you intended to use sesame seeds or knew Great-Uncle David hates seeds in his dentures so weren't using any this time.....they all ask YOU what they can do that is helpful.
(And have a list of all that you need to do, with timings, but also a mark against things that you are happy for others to do - whether you allocate those beforehand to make sure everyone helps or on the day to people who want to help).
You can also do lots beforehand that make it a little easier. I know some people prep their roast potatoes to the boiled/steamed, drained, basted and shaken stage and then freeze ready to just put straight into the oven; or make their gravy (Jamie Oliver's recipe has been mentioned more than once here!); or prep their sprouts or red cabbage dishes to just reheat on the day.
Making flavoured butter early is another good one - let butter soften at room temperature and add your seasoning(s) - pepper, garlic, herbs, lemon zest/juice, clementine zest, ….- you can do 2 or 3 different ones if you like to suit different things. Then once mixed, put the butter in the middle of some greaseproof paper, gently shape into approximately a log and then roll, twist the ends, store in fridge for a few days or freezer for a few weeks (or months in my house!).
Enjoy.
Don't forget to build in time to take a breather.
Make sure someone is on duty to keep the chef entertained (not everyone in another room) and watered (whether that's actual water, fizz, or any other beverage in between).