If you just want to quickly roast it, put it into a 400 F oven for about 20 minutes. Do you have a thermometer? The best way is to cook it until the temperature in the center is about 145 F.
What I would do is brown the outside of the roast in a hot skillet before putting it into the oven then cook it to the temperature given. The browning adds a lot of flavor and the stuff stuck to the pan makes a great gravy.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan