I am changing out a Robershaw unit with a Honeywell RTH3100C. The wiring on the Robertshaw was..

R - to RH
Y - to Y
G - to G
W - to W

Should they go as followed on the Honeywell?

R to R
Y to Y
RH to R
W to Aux

Thanks

Aux terminal is usually present on a heat pump thermostat. This may not be the right type for your system.