Put pork in crock pot and accidentally set to warm
There are a number of related questions regarding crockpots and food safety on this site but I found this informative link that will help explain why you may not want to risk keeping that roast that has been in a safety danger zone (below 165 F) for more than an hour.  The meat becomes a bacteria breeding ground, in essence.

http://culinaryarts.about.com/od/safetysanitation/p/slowcooksafe.htm