How to find out the voltage on Arduino ADC input?
I think you are approaching this the wrong way. You shouldn't be placing the resistor in parallel, rather you should be placing it in series. If you place them in parallel, you will only ever read a fixed 5v on one side or 0v on the other. You will then use the ADC on the Arduino to measure the voltage between the temperature sensors and the resistor.

What you are doing is creating a voltage-divider where the resistance of the temperature sensor is changing.

The equation become non-linear, so if you would like to make it simpler you can combine series and parallel as explained in this answer.