Level 1
Finally, I found how we can access comma-separated values by searching
->addColumn('role', function (User $user) {
return implode(', ', $user->getRoleNames()->toArray());
})
->filterColumn('role', function ($query, $keyword) {
$query->whereHas('roles', function ($q) use ($keyword) {
$q->whereRaw("roles.name like ?", ["%$keyword%"]);
});
})