I have and electrolux oven with the roasting option and convection?
continued prime rib
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A standing rib roast is among the easiest things to cook.
Regular and convection will work equally well. Convection is faster, but you won't get better results.
Use a "constant read" thermometer. Electrolux is pretty high up the food chain, and your stove may already include an electronic thermometer with front panel controls, or at least the option.
If you don't have a built in thermometer, the electronic probe types such as Polder and Pyrex are more convenient than the old, large, "meat thermometers." In addition to being more accurate and easier to read, they come with alarms to let you know when you've reached your target temp, and don't cost much either. Worth having.
There are several methods for cooking a standing rib, including "constant heat," "start hot, then cook very slow," "start hot for awhile, turn the oven off and let coast," etc. They'll all give you about the same results, but the cooking times will vary, and the slower methods tend to be more forgiving in terms of letting the roast go a little too long but more difficult to predict the timing for when to pull. Whichever method or cooking temperature, use a time/temperature chart to estimate your time; but rely on your thermometer for the final judgment.
With a large roast, you want to allow at least a twenty minute rest from oven to carve -- and more is better. The perfect, minimum rest and the exact amount of time it takes to cook a large Yorkshire pudding (or two) are magically the same.
If you're going to need a really long rest to make your party planning work, you can rest the roast in an insulated cooler for up to several hours.
If you need more advice, please don't hesitate to ask.
Given what you've likely already paid for meat, a probe with an alarm is highly recommended. Roasting large proteins doesn't get any easier. Try to get a look at whatever you buy though, my mom just got one for thanksgiving and I wasn't too happy with it. The target temperature couldn't really be set... instead one had to choose "Turkey" or "Beef" etc, and the temperatures associated with each was the USDA recommended temperatures which are pretty useless IMO.
Keep in mind that you should set your probe alarm well below your desired final temp, the prime will continue to cook once out of the oven. You might aim for as low as 120 internal temp to take out in order to end up at 130.