Oswalt, 35, was a free agent entering this season, so he may need some time to get conditioned well enough to contribute. The Rockies surely hope that, at worst, Oswalt can provide decent depth once he returns to form. Jhoulys Chacin has already spent some time on the DL this season and the health of Jorge de la Rosa, Juan Nicasio and Jon Garland certainly can't be guaranteed, considering their recent history. And while I think he deserves more time, Jeff Francis has been unimpressive so far. For a team leading its division, adding pitching depth makes all the sense in the world, especially at such a low risk.
Now the bad news. As most hardball fanatics are probably aware, Roy Oswalt had a lackluster season in 2012, but so did the Rockies and look where they are now! But seriously, his 5.80 ERA in nine starts and eight relief appearances for the Rangers last season aren't anything to jump up and down about, though he did manage a 59/11 K/BB ratio and under two walks per nine innings. Those low walk numbers are encouraging, although his propensity to give up the home run could limit his effectiveness.