Hi, there are several ways to validate the oil roasting process. one way to consider is using a surrogate organism from a certified lab that has a PA (Process Authority) to guide you. Another way is to use a data logger like the MOLE Gold which will require getting engineering involved to fabricate a caddy because the oil is too hot even for the thermal carrier.
again a PA is your best bet for the money. typically the amount of heat and dwell time FAR exceeds the levels from which to get a kill so oil roasting is not typically a CCP. meaning, just to get the quality characteristics desired, you have surpassed the kill requirements...
Again, your best bet is a PA. All of this information is easily found on the internet. The FDA has good information on PHF, Potentially Hazardous Foods and TCS foods that heated for period of time to be served.