I believe the Resistors would be sized ("size" = Resistance value - in Ohms), so as to allow the same level of Current that the "Wye" configuration does.
Example:
Motor's FLA = 130 Amps
Starting (Wye Connection) Ampere = +/- 75 Amps
Resistors are sized to allow +/- 75 Amps at rated Voltage.
I am not 100% sure on this, so let me find some references, then reply back.
Scott