restrict_specific_posts_to_specific_users.php

<? php
/**
 * Restrict post access to specific user IDs or user Roles.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function restrict_specific_posts_to_specific_users( $hasaccess, $thepost, $theuser, $post_membership_levels ) {

	/* SETTINGS */

	// Set your post/page id's here
	$posts_array = array( 2, 35, 156 );  // array elements must be integers and not strings

	// Set the user ID's that has exclusive access to these posts here
	$allowed_user_ids = array( 29, 121, 134 );

	// Set roles here that will receive access to all member content.
	$allowed_user_roles = array( 'editor', 'administrator' );

	/* END SETTINGS - No further editing required */

	// get the post ID
	$thepost_id = $thepost->ID;

	// Let's start by restricting these posts for everyone
	if ( in_array( $thepost_id, $posts_array ) ) {
		$hasaccess = false;
	}

	// Let's check if the user should have access to our custom restricted posts.
	if ( in_array( $theuser->ID, $allowed_user_ids ) ) {
		return true;
	}

	// This user's ID wasn't included in the allowed users array, let's check if they belong to an allowed role.
	foreach ( $allowed_user_roles as $key => $role ) {
		if ( in_array( $role, (array) $theuser->roles ) ) {
			//Give access if the user has an allowed role
			return true;
		}
	}

	return $hasaccess;
}
add_filter( 'pmpro_has_membership_access_filter', 'restrict_specific_posts_to_specific_users', 10, 4 );

Users can also be redirected from custom restricted posts using the template_redirect hook.
https://gist.github.com/ipokkel/caa9e743a1e6c1fe711732c5cc077ea9