You must have a meat thermometer. the instant read digital type I have found to be preferable (Taylor is a good brand). However, my favorite is the type with a probe that you insert into the meat and then run the cable out of the oven (you shut the door, no heat loss)and connect it to a digital readout/timer. The advantage is that you don't have to keep opening the door (with heat loss) to check the temp. Also you get a continuous temp readout so you don't overcook. And, you can set the timer to go off when a certain temp is reached.
Uhh , get one , dude . It's the only way to be sure . And it still takes some practice . ( Bummer , eating " practice " roast beef , heh heh . ) I do mine low temp first , up to an internal temp of about 115 , and then crank up the oven to broil ( 500 or so ) to brown the outside and bring the inside up to about 125 or 130 . I would check a cookbook about these temps , as it's late and I don't remember off the top of my head what temp is for what meat , but it's easy either way . A decent meat probe should last at least 10 years or so , totally worth the investment , they cost like 20 bucks or so .
I cooked roast beef last weekend successfully, using the following method:
1. Buy a good roast. We bought eye of round, which is a cheaper cut, but is dense and has lots of flavour.
2. Bring it to room temperature. We put it in a plastic bag with some five spice powder and some chipotle powder. Five spice is especially good.
3. Preheat the oven to 425. Once the oven is heated, put the roast in. I like it being suspended, so we cooked it on a rack over a roasting pan.
4. Roast for 15 minutes, then turn the oven down to between 350 and 375 (we had it at 370). Roast for 18 minutes per pound. At this stage a 3 pound roast was was 130 degrees.
5. Take it out, and let it rest for at least 15 minutes. The roast was medium rare (pink).
A meat thermometer helps (especially an instant one) and most importantly, an oven thermometer. I found that if you roast beef in the oven to 140 it's actually well done as opposed to medium.
Actually, this method (except it was salt, pepper, onion powder, etc.) and cut was what I grew up with as "roast beef." My mom would then deglaze the pan to make au jus.
It is good, but I think the more classic approach of searing in a heavy pan and then slow roasting at 250-275 (or, if you have the time, the 200-225 recommended by some of the other posters) produces more of the melting meat with beautiful crust approach that is the sine qua non of roast beef (though eye round, a cut that some find useful only for braising but that I actually like because I was reared on it, will only get so tender....).
The secret is slow cooking. My cousin had a restuarant famous for its prime rib...he put it on in the morning, to serve for dinner. Very, very slow oven. (about 200 or less). You might have to experiment. I do a cross rib roast on a gas grill with one burner on absolute low. It helps to monitor the doneness with a thermo, but with practice you can tell with a knife tip on your lower lip. I marinate my for 2-3 days in a teriyaki type marinade.
The meat thermometer is absolutely key. Getting a good instant read (I like digital) will be your best investment. Remember to take the roast out before it reaches the desired temp and to let it sit to finish cooking on the counter. This will make sure that all the juices don't rush out in the first cut leaving the rest of the roast dry. Exactly how much before the final temp you take the roast out is dependent on it's size. I like to finish at medium rare (140-145) so will take out a 3-4 lb roast at 120-125. It does depend on the cut as well - denser, leaner meat will take longer and will also cook to a somewhat higher temp after the heat is removed. E.g. - tenderloin is denser than a rib roast. There are various ways to flavor the meat and other techniques to create a tasty crust - that's all up to you - but the only thing I would consider absolutely mandatory is salting the meat and rubbing it in well. My advice is to get used to working with one cut and doing that well, before trying lots of others. Having said that, don't make that first cut a difficult one. A nice rib roast would be a lot tastier than a round (more expensive as well). Certain cuts are definitely going to be lean and drier - if you do eye-of-round, expect to make some au-jus or a full-throttle gravy (which you have to have for the creamed garlic mashed potatoes) sorry - that doesn't go with the sandwich theme...
Well, I don't know what cut you are using, so I can only offer the classic tried-and-true method:
Do not cook immediately after removing from the frig, but instead bring the roast to room temperature (failing to do so is the single most common reason that the interior is raw while the outer layers are almost well done). Season liberally with salt and pepper. Preheat the oven to a slow-moderate range, like 275 degrees.
Heat a heavy pan on the stovetop over fairly high heat; add some olive oil (you can add a little butter if you prefer, but be careful to avoid scorching) and sear and brown all the sides. Remove from the stove top and place in the oven and cook until your desired temperature.
This classic sear-first/slow-roast method generally produces the most reliable results in my experience. But only if you bring the roast up to a proper temperature beforehand....