Their rotation is nothing special if you ask me. I don't think CC is an ace, Westbrook faded a little last year. Lee is a solid number 3 or 4 type along with Byrd. With all of this said they don't have a great rotation, IMO they have about 3 number 3's and 2 5's. All of their pitchers are big league level pitchers, just nothing great.
Just my 2 cents.
They do have Sowers who is close to MLB ready and Miller who is about a year away in the minors to help with the rotation in the future. It is doubtful that these 2 help this year, but they will form a nice 1,2 punch in the future.