According to this article in the Post, the pitchers the Rockies are looking at this offseason include the following:
None of the five are exactly spring chickens, although all five probably have a serviceable year or two left in the tank. If you follow the links you'll note that according to the park adjusted ERA+ stat at Baseball Reference, three of the five profile as within a tick or two of league average (100) throughout their careers, with the exception of Estes and Johnson, who have been about ten percent off that mark.
Estes and Astacio have the intangible of being "proven winners" at Coors Field in their favor, although in Estes' case this was as much a function of luck as anything, and in Astacio's case, this was a function of us having a good pitcher at his peak. All told, I think I like Dessens best if I had to pick just one, but I would definitely shy away from Estes and Johnson and wouldn't mind seeing Helling or the return of little Pedro.