A lot depends on the cut of beef... but try this:
Cut a few 1/4 inch deep slits on the top of the beef cut... (fat side). Insert about 3 or 4 cloves of garlic in the slits. Salt and pepper the cut using coarsely ground fresh pepper. Pre-heat oven to 350 degrees F (sorry, I'm in the U.S.). Place the beef, again, fat side up directly on the oven rack neer the middle. Place a shallow drip pan undeneath. This will set a convection current and you won't have to turn the roast. The melting fat on top will keep the cut moist.
Roast it at 350 degrees (or the equivalent C temp) for one hour. Now, the important part... you need a good meat thermometer and the best kind will be the remote reading type so one doesn't have to open the oven until the end. Place the temometer in the thickest portion, half way through. Lower the temperature to 225 F and continue roasting until the internal temp is 135 to no more than 140 degrees F, probably 2 or 3 hours depending on the thickness, for medium rare. Remove it, cover with a tent of aluminum foil and let it rest at least 20 minutes before carving.
You've saved the drippings in the pan haven't you? So here's the sauce recipe:
Remove the dripping pan from the oven and place on the stove top at medium heat. Add some water, 1/4 cup red wine (drinking wine, not cooking wine),and maybe half a cup of beef stock to the drippings to deglaze (loosen the drippings from the pan). Dissolve a tablespoon of cornstarch in a little cold water and add to the drip pan. Stir quickly while the gravy thickens to avoid lumping. You can add a little butter if there is not a lot of fat in the drippings. Add salt and pepper to taste. We serve ours with some fresh rosemary and always fresh ground horseradish... Best of luck!