You should be able to put the phone in lockdown mode. Settings/lock screen and AOD/secure lock settings. Enter your pin/password and turn on show lockdown option. This will put an extra option on the power off screen called lockdown. Tapping this will immediately lock your phone and turn off biometrics. You will need to enter your pin or password to unlock the phone. If you use extend unlock, you can also enter lockdown mode by long pressing the open lock icon on the top of the lock screen. I am not sure pressing the lock on a locked lock screen will turn off the biometrics, but it's worth a try. However, if someone has control over your phone, it's doubtful that you will have the time to react (especially if you are deceased or unconscious) to turn the feature on. If you are that concerned about the possibility, you should just keep the biometrics off. If you don't trust your housemate while you are sleeping, that's a whole other can of worms.
