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Please, please don’t cover your rib roast! Your covered roaster will do great for chuck or pot roasts but a beautiful rib roast deserves to be done differently.
I make a rub of salt, fresh ground pepper, thyme, and minced fresh garlic and rub it on the outside of the meat. You can use any herbs you like on your beef – I have used rosemary and summer savory, too but I like thyme best. I never measure the amounts – I’m one of “those” cooks that only measures when I have to…
I have always had luck by allowing the roast to come to room temperature and then starting it in a 500-degree oven for 20 minutes (this seems to seal the outside of the meat and keeps the juices in) and then turning the heat down to 350 and finishing cooking at that temperature.
The timing depends on how well done you like your meat.
I like mine rare, so it is about 23 to 25 minutes per pound (always include the time it was cooked at 500-degrees in the calculations, too)
for medium rare, it is about 24 to 28 minutes a pound;
for medium it is 27 to 30 minutes a pound;
med well is 28 to 34 per pound.
If you aren’t familiar with roasting meats you should use a meat thermometer to verify how well the meat is cooked. .I usually don’t open the oven until it is time to put in the potatoes or anything else I have to go in. Good luck!