The Denver Post's Troy Renck lists Aaron Cook as one of the pitchers the Rockies are interested in signing to a minor league deal.
Renck also mentions Derek Lowe, Chris Volstad and Jeff Karstens. Karstens will almost surely require a guaranteed deal, something the Rockies would prefer not to offer, and Lowe probably would, as well. Volstad and Cook might be available on minor league deals, though. Cook, of course, spent the first 10 seasons of his career with the Rockies. He posted a 5.65 ERA over 18 starts for the Red Sox in 2012.