$previousOwners = $this->userRepo()->hasRoles(['Owner'])->pluck('id')->toArray();
$newOwners = $this->clinic_owners;
$deleted = array_diff($previousOwners, $newOwners);
$new = array_diff($newOwners, $previousOwners);

foreach ($deleted as $id) {
    $user = $this->userRepo->find($id);
    $user->removeRole('Owner');
}

foreach ($new as $id) {
    $user = $this->userRepo->find($id);
    $user->assignRole('Owner');
}