OK this is how I do a roast.
Meat in the slow cooker from early, I'm usually awake before 6.00am. Then just leave it.
Peel potatoes and prep the veg. I have an electric steamer so I prep and put the veg (except the potatoes) in that. Unless I'm doing carrot and swede mash - I boil it into submission. Veg in the steamer takes about 15 mins.
About an hour before you intend to eat put a large oven dish / tray - make sure you use a metal one in the oven, put the fat in, ideally you want animal fat as it gets hotter than oil but you have a vegi so either do a few in a different dish or use oil.
Leave to heat for 10-15 mins, you want the fat smoking. Then put the potatoes in the dish, use a spoon to make sure they are covered in fat and leave them alone for 15 mins.
Open the oven and turn the potatoes over and put fat in your Yorkshire pudding tray which should be in the top of the oven and let that heat for about 10 mins.
Pour the YP batter in the tin. At this point I would take the meat out to rest and make gravy in the slow cooker but I think buying a vegi gravy so heat that now.
Switch the steamer on.
Cut the meat up and put in a serving dish/plate I usually put the roasts with the meat, put the veg on another serving dish and bring them both to the table, put the gravy in a jug / boat and call everyone in.
OK
After all that for a suggestion for a different meal how about a raclette? Stick it in the middle of the table with dishes of veg and some boiled new potatoes and cheese slices.
You can also serve eggs to cook in the trays, passata also works. Put some raw meat on the table, for a big group I would maybe do two different meats, maybe marinade some chicken and serve slices of beef.
The beauty of this is that everyone cooks their own food at the table. You tend to cook a bit, eat a bit, cook a bit more.
You can get a really small one for the veggi person to use.