Simple WordPress login redirect. Can be used as a mu-plugin or in functions.php

brg_login_redirect.php

<?php

function brg_login_redirect( $redirect_to, $request, $user ) {
  global $user;
	//if there's a user with defined roles
	if ( isset( $user->roles ) && is_array( $user->roles ) ) {
	  //check if it's admin 
		if ( in_array( 'administrator', $user->roles ) ) {
		  //admins can go anywhere
			return $redirect_to;
		} else {
		  //non-admins go to home
			return home_url();
		}
	//there's no user roles to check
	} else {
	 //go home
	  return home_url();
	}
}
add_filter( 'login_redirect', 'brg_login_redirect', 10, 3 );