Roast
Heat the oil in a skillet over medium heat. Add the roast and cook until brown on all sides; drain. Place onion and sweet potatoes in a 4-quart slow cooker; top with the roast. Combne the broth and seasonings; pour over the roastl Cover and cook on low setting for 7 to 8 hours or on high setting for 4 to 5 ours.

Remove roast from cooker and reserve the juice. Place roast on a serving platter, surrounded  with vegetables; keep warm

Gravy
Combine the corstarch and water in a small saucepan; add one cup of juices from the slow cooker. Cook and stir over medium heat until thickened and bubbly; continue cooking and stirring 2 more minutes. Serve gravy on the side with roast.

Note: A good vegetable side is suggeste; asparagus or broccoli, asparagus shown in photo.