Railworks America

Is there a way to set loco's with thier engines off in a free roam but keep them player driveable so one can select it and start it up?

The only way I could see possible would be if you were to conceal a fuel marker under the ground, put a loco with no fuel in it over top of the marker, and hen in play, push T to refuel, then start it up when full. Of course, this would require you modify the route however.

I think David Brindley's expert mode models will allow you to do this. Of course you also need to know how to turn them on, and drive them. You can find several repaints in the RWA library (GP7, GP15, F40PH).