Resistor in RC snubber
Snubbers are energy-absorbing circuits used to suppress the voltage spikes caused by the circuit's inductance when a switch,electrical or mechanical, opens. and may also cause false triggering of the device (relay or thyristor) 

The snubber capacitance has to meet two requirements. 
 First, the energy stored in the snubber capacitor 
must be greater than the energy in the circuit's inductance. 

Secondly, the time constant of the snubber circuit should be small compared to the shortest on time 
expected, usually 10% of the on time. 

consider the case When  the  transistor  switch  opens,  the  snubber 
capacitor looks like a short to the voltage change, 
and only the snubber resistor is in the circuit. Choose a  resistor  value  no  larger  than  the  characteristic impedance of the circuit so that the inductive current to be snubbed can continue unchanged without a voltage transient when the switch opens.
and R is also helps in power dissipation when the switch is open as C alone cannot do it.

hope this helps