style.css is a requirement for any theme. Therefore you cannot dequeue it. You can however have a blank (except for the comments) style.css and enqueue another stylesheet for certain templates. To do so you would use wp_enqueue_scripts() like so :
function my_enqueue_style() {
if ( is_front_page() ) {
wp_enqueue_style( 'mystyle', get_stylesheet_directory_uri() . '/mystyle.css' );
}
}
add_action( 'wp_enqueue_scripts', 'my_enqueue_style' );