This root does not seem to be attested in Arabic: Arb.
rwḍ ‘to train a
riding beast’ is quite remote both phonetically and semantically
The widespread equation with Akk.
râṣu ‘to come to help’ is semantically uncertain, even if the meaning shift “to run” > “to help”
is sufficiently well attested in Indo-European (Buck 1949:1353‒1354)