Just pass the user id to this function:
function get_role($user_id)
{
if(is_int($user_id))
{
$user = new WP_User( $user_id );
if ( !empty( $user->roles ) && is_array( $user->roles ) )
{
foreach ( $user->roles as $role )
echo $role;
}
}
else
echo "Something else";
}