  We classify the rational solutions of the Sasano systems of types
$B_4^{(1)},$ $D_4^{(1)}$ and $D_5^{(2)},$ which are all given by the coupled
$P_{\rm III}$ systems and have the affine Weyl group symmetries of types
$B_4^{(1)},$ $D_4^{(1)}$ and $D_5^{(2)}.$ The rational solutions are classified
as one type by the B\"acklund transformation groups.
