Oscillator circuits operation?
The Colpitts circuit, like other LC oscillators, consists of a gain
  device, such as a transistor or vacuum tube, with its output connected
  to its input in a feedback loop containing a parallel LC circuit
  (tuned circuit) which functions as a bandpass filter to set the
  frequency of oscillation.
  --Wikipedia


This is a Colpitts' oscillator (most common form; there are several):



I think you are being confused by the bias resistors. They do not play a role in the AC (oscillating) operation of the circuit (to the first order).

Here it is again with the biasing removed/simplified:



The oscillator works by applying amplification (positive feedback) via the transistor and using an LC circuit as a filter to set the frequency of oscillation. There are no RC interactions in the ideal case.