After having root canal more than a week ago, I still feel minor swelling in the face. Overall, I feel so much better. Is the swell time common?

Not usually . A week is a little bit too long in my opinion., I guess the better question would be was it swollen prior to your root canal? Root canals remove the inflamed or infected nerve, artery and vein in the tooth. Afterwards it is hermetically sealed by the filling material which ensures a good deal and prevents bacteria from circulating to and from the tooth through the passages to the tooth. .
It happens. Without knowing if you had an infection or if you were swollen before the procedure it is hard to answer your question. Sometimes the infection/irritation takes longer to resolve that you expect. If of great concern, speak to the dentist who performed the procedure.