I'm in the Springs so I'm not that much help. Getting your IV cert is pretty essential to work. A basic EKG class might help too, that seems to be less of a big deal. ICS 100, 200, 700 (and maybe 800) are often also required, you can take them for free online. Not too hard.
In terms of places to work...Denver Health does hire EMTs, but I'm not too sure on how they're used. Falck does Aurora. AMR does mostly transfers with some backup 911 as well as the 911 in Golden, Longmont, and Boulder. ActionCare does mostly transfers with some backup 911. Places that I know much less about: iCare (does almost all flight team transfers from Centennial airport), Apex (newer company, better reputation based on management's credentials), Northglenn (transfers in Denver, 911 in Commerce City). Places I know nothing about: Mile High, Western, Mountain States, Stadium.