Pull current roblox dmg, then extract the app.

pull-app.sh

#!/bin/sh

# obtain the current client version string
VERSION="$(curl  -fLs 'https://clientsettings.roblox.com/v2/client-version/MacPlayer' | grep -Eho 'version-.{16}')"

# test VERSION var, if zero, exit with a log
[ -z "$VERSION" ] \
    && printf '%s\n' 'Unable to pull current version string. The dependent service may be down, or your proxy denies connections to it.' \
	&& exit 1

# download the latest binary dmg
curl -fLOs "https://setup.rbxcdn.com/mac/$VERSION-Roblox.dmg"

# mount the volume
hdiutil attach -quiet -nobrowse ./*-Roblox.dmg

# extract the .app from attached disk
# optional: extract to provided directory
cp -r /Volumes/RobloxPlayerInstaller/*.app "./$1"

# unmount the volume
hdiutil detach -quiet /Volumes/RobloxPlayerInstaller

# delete dmg file
rm -f ./*-Roblox.dmg

# success
printf '%s\n' 'done'