  Links between the properties of radio-loud active galactic nuclei (RLAGNs)
and the morphology of their hosts may provide important clues for our
understanding of how RLAGNs are triggered. In this work, focusing on passive
galaxies, we study the shape of the hosts of RLAGNs selected from the Karl G.
Jansky Very Large Array Cosmic Evolution Survey (VLA-COSMOS) 3GHz Large
Project, and compare them with previous results based on the first data release
(DR1) of the LOFAR Two-Metre Sky Survey (LoTSS). We find that, at redshifts of
between 0.6 and 1, high-luminosity ($L_{1.4 GHz}\gtrsim10^{24}\rm W Hz^{-1}$)
RLAGNs have a wider range of optical projected axis ratios than their
low-redshift counterparts, which are essentially all found in round galaxies
with axis ratios of higher than 0.7. We construct control samples and show that
although the hosts of high-redshift RLAGNs with the highest luminosities still
have a rounder shape compared with the non-RLAGNs, they on average have a
smaller axis ratio (more elongated) than the local RLAGNs with similar stellar
masses and radio luminosities. This evolution can be interpreted as a byproduct
of radio luminosity evolution, namely that galaxies at fixed stellar mass are
more radio luminous at high redshifts: artificially increasing the radio
luminosities of local galaxies ($z\leq$0.3) by a factor of 2 to 4 can remove
the observed evolution of the axis ratio distribution. If this interpretation
is correct then the implication is that the link between AGN radio luminosity
and host galaxy shape is similar at $z\simeq1$ to in the present-day Universe.
