How long and at what oven temperature should you heat the prepared roast beef.and ham dinner?

I would say low heat 350 for 20-25 minutes

Be sure the prime rib comes to room temperature before you put it in the oven prior to that preheat the oven to 275 and put all the goodies in the oven for approximately 20 to 25 minutes then and place the prime rib in probably the last five or six minutes covered and the ham maybe the last 8 to 10 minutes covered and you should be good to go Merry Christmas...And be sure to heat up the Au Jus separately... please enjoy your meals! 😊