Keep your oven clean
Use the correct size dish. Do not overfill the dish and make allowance for boil over.
Use a Roasting bag. This retains the moisture in your roast and eliminates splatter of grease and fat throughout your oven/
Using a lid will have the same effect as a roasting bag.
Clean up any mess ASAP. before it carbonates.
Place a tray on the bottom rack of the oven (not the floor), for easy removal and cleaning.
You can always use the BBQ. Don't forget Magic Oven & Windows clean those too.