Roasted Sweet Potatoes with Cumin and Cilantro

2 orange-fleshed sweet potatoes, about 1 lb. total, peeled  

1 Tbs. canola or safflower oil  

1 tsp. ground cumin 

1/2 tsp. kosher salt 

Freshly ground pepper, to taste 

2 Tbs. finely chopped fresh cilantro