Kind of depends on the type of roast... however...
Try this as it always works for me (be it prime rib or bottom round).
Pre heat oven to 550 (F) degrees for at least 30 minutes to make sure it is nice and TOASTY...
Take roast out of fridg and put on counter for at least an hour.
Dry off with paper towels.
Make a paste of 1/4 cup dijon mustard, salt, pepper, fresh chopped garlic and a little olive oil.
Rub all over roast.
Put in oven for 10 minutes to sear, then lower the temp to 325 (F) for about 20 mins per pound.
Makes a nice and tasty roast.