Can you take pain pills while on shrooms?

No, it is never advised to mix drugs - the reaction you get may not be the reaction you are hoping for.

Assuming your pills are opiates you can safely take them with psilocybin active mushrooms although it's not recommended as though it can sully the trip. You will not want to have your consciousness dampened by opiates whilst on shrooms. Taking the pills at the very tail end of the trip could be viable but that being said many find that smoking marijuana on the come down produces opiate-like effects so that would be a preferred substitute.