The truth is, I'd love to buy an amazing beef roast to eat whenever I wanted to. The reality is, it's hard to spend the 50-100 bucks it takes to get a decent cut of meat (e.g., strip roast).
So here is what you do. You buy the cheap crap. Rump roast, whatever. You prep it and cook it right.
Here is what you don't do: take the thing out of the fridge and toss it in a 400F oven for 3 hours. You might as well go chew on an old leather shoe.
step 1: buy something. You can get a top or bottom round roast for a reasonable price. Today I bought one got one free. 12 bucks.
step 2: dry aging. Yep, back to that again. Stick it in the back of your fridge UNCOVERED for 3-5 days. Yes, it will shrink. Yes it will get hard and crusty on the outside. It's supposed to do that. It will taste better. Honest.
step 3: take it out of the fridge and carve all the crusty hard bits off. Don't carve off all the fat on the outside. You'll need that later.
Step 4: let it warm up on the counter for at least an hour. Don't ever put a cold roast in a hot oven. The thing will never cook right. Would you cook it frozen? There had better only be one answer out of your face on that one.
Step 4: preheat the oven to 225F. Yep, you got it...slow and slower is the way to cook this sucker.
step 5: Pat the meat completely dry. dry dry dry. Rub some freshly ground pepper on it.
step 6: heat a hot skillet with some olive oil in it. Sear each side of the roast for at least 2 minutes on med-high, or until you end up with a decent crust. When your done either use the pan you've got if it is oven safe, or find a new pan/dish.
step 7: A THERMOMETER WITH AN ALARM and probe goes into the meat. Spend the 25 bucks. You should always be cooking to temperature anyway, not time. Set the alarm temp to 130F. OK, 140F if you're a real pussy. Any higher than that and you're wasting your time.
step 8: in the oven. Fat side UP, if you have any. Remember step 4? 225F.
step 9: wait. wait. wait. The alarm will go off. Take the thing out of the oven, and cover it for 10-15 minutes. This part is important. Don't skip it.
While the roast is resting for 10-15 minutes, make up a mix of softened butter, crushed garlic, and whatever spices you fancy. You can try oregano, dill, basil, thyme, whatever. If you don't know what to do, then mix up a few batches and give them a taste. Pick one you like.
Spread it onto the top of the roast while it's resting. When your 10-15 minutes are up, slice the roast AGAINST THE GRAIN. That part is important too. Muscle fibers are long. If you cut with the grain you'll be chewing all night long.