I always did a big plate of sandwiches (Quartered), left em with a damp teatowel draped over a plate of cakes too and settled down to watch 'Sunday night at the London Palladium, (7pm) everyone helped themselves as and when.
Roasts are usually bigger than other meals during the week (well for me anyway) so you probably don't need tea as well. If I get hungry later on there is usually some leftovers to nibble on.
We used to have yorkshire puddings and gravy seperate to our roast dinner so were too full for anything afterwards. About 5 ish we sat down to trifle and a piece of cake - that was the best part in my opinion at the time.