Presuming it's a joint I'd do this:
Brown the joint on the top of the stove to get some colour (not to 'seal in the juices' - that's a complete myth). Season with plenty of salt and black pepper as you turn the joint in the pan - this will help your gravy later.
In a roasting tin put some roughly chopped onion, carrot, leek, celery (any or all of these) plus a clove or two of garlic, a bay leaf, and a sprig of rosemary and/or thyme. Toss this lot in a tbsp or two of oil.
Place the seared joint on the veg and put in a medium oven (gas 5/6, 190-200C). Time depends on how you want to eat it - rare, 15mins/lb plus 15 mins; medium, 20mins/lb plus 20 mins. Well done=ruined in my book but if you want it well done, cook for 25mins/lb plus 25 mins. Baste the joint every 30 mins or so with the juices in the pan.
When cooked, remove joint and put on a warm plate to rest for 20 mins, covered with foil. This will give you a chance to make your gravy - take a potato masher to the veg in the pan, and give it a good pounding. Before you add any liquid, mix in a tbsp or two of plain flour and put the tin on the top of the stove on a medium heat. Cook the roux you've just made for 5-10 mins, stirring often, and then add a glass of red wine, plus any water from veg you're serving (or stock, or just plain old water). Reduce by a third, check the seasoning, strain, and you're done. If you wanted to be really cheffy, you could put the strained gravy into a clean pan and finish it with a teaspoon or two of butter, which would give it a nice sheen and extra richness.
Hmmm. Hungry now...