Conditionally toggle Free Shipping based on the user's role and contents of the cart

wc-ninja-free-shipping-for-a-user-role.php

function wc_ninja_free_shipping_for_a_user_role( $rates, $package ) {
 	
 	// Only modify rates if free_shipping is present
  	if ( isset( $rates['free_shipping'] ) ) {

  		// Add a user role specific capability here
  		if ( ! current_user_can( 'manage_woocommerce' ) ) {
  			// Cart Subtotal
  			$subtotal = WC()->cart->subtotal;
  			// Number of products in the cart
  			$count = WC()->cart->cart_contents_count;

  			// Add some optional conditions here using $subtotal and $count
  			if ( $count >= 50 || $subtotal >= 150) {
  				unset( $rates['free_shipping'] );
  			}
  		}

	}
	
	return $rates;
}
add_filter( 'woocommerce_package_rates', 'wc_ninja_free_shipping_for_a_user_role', 10, 2 );